MySQL Reference Manual for version 3.23.37.

1 General Information About MySQL

This is the MySQL reference manual; it documents MySQL Version 3.23.37. As MySQL is work in progress, the manual gets updated frequently. There is a very good chance that this version is out of date, unless you are looking at it online. The most recent version of this manual is available at http://www.mysql.com/documentation/ in many different formats. If you have a hard time finding information in the manual, you can try the searchable PHP version at http://www.mysql.com/documentation/manual.php.

MySQL is a very fast, multi-threaded, multi-user, and robust SQL (Structured Query Language) database server.

MySQL is free software. It is licensed with the GNU GENERAL PUBLIC LICENSE http://www.gnu.org/. See section 3 MySQL Licensing and Support.

The MySQL home page provides the latest information about MySQL.

The following list describes some useful sections of the manual:

For information about the company behind MySQL, see section 1.2 What Is MySQL AB.
For a discussion of MySQL's capabilities, see section 1.6 The Main Features of MySQL.
For installation instructions, see section 4 Installing MySQL.
For tips on porting MySQL to new architectures or operating systems, see section I Comments on porting to other systems.
For information about upgrading from a Version 3.22 release, see section 4.18.1 Upgrading From Version 3.22 to Version 3.23.
For a tutorial introduction to MySQL, see section 9 MySQL Tutorial.
For examples of SQL and benchmarking information, see the benchmarking directory (`sql-bench' in the distribution).
For a history of new features and bug fixes, see section F MySQL change history.
For a list of currently known bugs and misfeatures, see section G Known errors and design deficiencies in MySQL.
For future plans, see section H MySQL and the future (The TODO).
For a list of all the contributors to this project, see section E Credits.

IMPORTANT:

Reports of errors (often called bugs), as well as questions and comments, should be sent to the mailing list at mysql@lists.mysql.com. See section 2.3 How to Report Bugs or Problems. The mysqlbug script should be used to generate bug reports. For source distributions, the mysqlbug script can be found in the `scripts' directory. For binary distributions, mysqlbug can be found in the `bin' directory. If you have found a sensitive security bug in MySQL, you should send an email to security@mysql.com.

If you have any suggestions concerning additions or corrections to this manual, please send them to the manual team at docs@mysql.com.

This is a reference manual; it does not provide general instruction on SQL or relational database concepts. If you want general information about SQL, see section 1.9 General SQL Information and Tutorials. For books that focus more specifically on MySQL, see section 1.5 Books About MySQL.

1.1 What Is MySQL

MySQL, the most popular Open Source SQL database, is provided by MySQL AB. MySQL AB is a commercial company that builds its business providing services around the MySQL database. See section 1.2 What Is MySQL AB.

MySQL is a database management system.: A database is a structured collection of data. It may be anything from a simple shopping list to a picture gallery or the vast amounts of information in a corporate network. To add, access, and process data stored in a computer database, you need a database management system such as MySQL. Since computers are very good at handling large amounts of data, database management plays a central role in computing, as stand-alone utilities, or as parts of other applications.
MySQL is a relational database management system.: A relational database stores data in separate tables rather than putting all the data in one big storeroom. This adds speed and flexibility. The tables are linked by defined relations making it possible to combine data from several tables on request. The SQL part of MySQL stands for "Structured Query Language" - the most common standardized language used to access databases.
MySQL is Open Source Software.: Open Source means that it is possible for anyone to use and modify. Anybody can download MySQL from the Internet and use it without paying anything. Anybody so inclined can study the source code and change it to fit their needs. MySQL uses the GPL (GNU General Public License) http://www.gnu.org, to define what you may and may not do with the software in different situations. If you feel uncomfortable with the GPL or need to embed MySQL into a commercial application you can buy a commercially licensed version from us.
Why use MySQL?: MySQL is very fast, reliable, and easy to use. If that is what you are looking for, you should give it a try. MySQL also has a very practical set of features developed in very close cooperation with our users. You can find a performance comparison of MySQL to some other database managers on our benchmark page. See section 13.7 Using Your Own Benchmarks. MySQL was originally developed to handle very large databases much faster than existing solutions and has been successfully used in highly demanding production environments for several years. Though under constant development, MySQL today offers a rich and very useful set of functions. The connectivity, speed, and security make MySQL highly suited for accessing databases on the Internet.
The technical features of MySQL: For advanced technical information, see section 7 MySQL Language Reference. MySQL is a client/server system that consists of a multi-threaded SQL server that supports different backends, several different client programs and libraries, administrative tools, and several programming interfaces. We also provide MySQL as a multi-threaded library which you can link into your application to get a smaller, faster, easier to manage product.
MySQL has a lot of contributed software available.: It is very likely that you will find that your favorite application or language already supports MySQL.

The official way to pronounce MySQL is ``My Ess Que Ell'' (not MY-SEQUEL). But we try to avoid correcting people who say MY-SEQUEL.

1.2 What Is MySQL AB

MySQL AB is the Swedish company owned and run by the MySQL founders and main developers. We are dedicated to developing MySQL and spreading our database to new users. MySQL AB owns the copyright to the MySQL server source code and the MySQL trademark. A significant amount of revenues from our services goes to developing MySQL. See section 1.1 What Is MySQL.

MySQL AB has been profitable providing MySQL from the start. We don't get any outside funding, but have earned all our money ourselves.

We are searching after partners that would like to support our development of MySQL so that we could accelerate the development pace. If you are interested in doing this, you can email partner@mysql.com about this!

MySQL AB has currently 20+ people on its payroll and is growing rapidly. http://www.mysql.com/development/team.html.

Our main sources of income are:

Commercial high quality support for MySQL provided by the MySQL developers themselves. If you are interested in purchasing a support contract, please visit https://order.mysql.com/ to view our support options or to order support.
Consulting services. We have developers and consultants in 12 countries and partners in many other countries that can help you with almost any MySQL related issues. If you need consulting services, please email a good description of your needs to info@mysql.com! If we can't handle this ourselves we can usually find a partner or a developer that can help you with your problems.
We sell licenses for using MySQL as an embedded database. See section 3.4 MySQL Licensing and Support Costs. If you have a commercial product for which you need a fast, high quality database, but you can't afford to make your product Open Source, you can buy the right to use the MySQL server under a normal commercial copyright. If you are interested in this you can buy MySQL licenses at https://order.mysql.com/ or contact us at licensing@mysql.com.
Advertising. http://www.mysql.com/ is a very popular web site with more than 10,000,000 page views per months (January 2001). By putting a banner on this you are guaranteed to reach a lot of potential customers in the Open source, Linux and database community. If you are interested in this email advertising@mysql.com.
We are building a partner program to be able to provide MySQL services in every country. If you are interested in becomming a partner of MySQL AB please visit http://www.mysql.com/information/partners.html or email partner@mysql.com.
We provide MySQL training through our partner programs. For more information, please email info@mysql.com.
The MySQL brand has, since 1995, been associated with speed and reliability, and is known to be something you can depend upon. If you are interested in using the MySQL trademark in your marketing, you can email info@mysql.com about this.

The MySQL core values show our dedication to MySQL and Open Source.

We want MySQL to be:

The best and the most used database in the world.
Available and affordable for all.
Easy to use.
Continuously improved while remaining fast and safe.
Fun to use and improve.
Free from bugs.

MySQL AB and the people of MySQL AB:

Promote Open Source Philosophy and support the Open Source Community.
Aim to be good citizens.
Prefer partners that share our values and mind-set.
Answer mail and give support.
Are a virtual company, networking with others.
Work against software patents.

1.3 About This Manual

This manual is currently available in Texinfo, plain text, Info, HTML, PostScript, and PDF versions. The primary document is the Texinfo file. The HTML version is produced automatically using a modified version of texi2html. The plain text and Info versions are produced with makeinfo. The Postscript version is produced using texi2dvi and dvips. The PDF version is produced with pdftex.

This manual is written and maintained by David Axmark, Michael (Monty) Widenius, Jeremy Cole, and Paul DuBois. For other contributors, see section E Credits.

1.3.1 Conventions Used in This Manual

This manual uses certain typographical conventions:

constant: Constant-width font is used for command names and options; SQL statements; database, table and column names; C and Perl code; and environment variables. Example: ``To see how mysqladmin works, invoke it with the --help option.''
`filename': Constant-width font with surrounding quotes is used for filenames and pathnames. Example: ``The distribution is installed under the `/usr/local/' directory.''
`c': Constant-width font with surrounding quotes is also used to indicate character sequences. Example: ``To specify a wild card, use the `%' character.''
italic: Italic font is used for emphasis, like this.
boldface: Boldface font is used for access privilege names (for example, ``do not grant the process privilege lightly'') and occasionally to convey especially strong emphasis.

When commands are shown that are meant to be executed by a particular program, the program is indicated by a prompt shown before the command. For example, shell> indicates a command that you execute from your login shell, and mysql> indicates a command that you execute from the mysql client program:

shell> type a shell command here
mysql> type a mysql command here

Shell commands are shown using Bourne shell syntax. If you are using a csh-style shell, you may need to issue commands slightly differently. For example, the sequence to set an environment variable and run a command looks like this in Bourne shell syntax:

shell> VARNAME=value some_command

For csh, you would execute the sequence like this:

shell> setenv VARNAME value
shell> some_command

Often, database, table, and column names must be substituted into commands. To indicate that such substitution is necessary, this manual uses db_name, tbl_name and col_name. For example, you might see a statement like this:

mysql> SELECT col_name FROM db_name.tbl_name;

This means that if you were to enter a similar statement, you would supply your own database, table, and column names, perhaps like this:

mysql> SELECT author_name FROM biblio_db.author_list;

SQL statements may be written in uppercase or lowercase. When this manual shows a SQL statement, uppercase is used for particular keywords if those keywords are under discussion (to emphasize them) and lowercase is used for the rest of the statement. For example, you might see the following in a discussion of the SELECT statement:

mysql> SELECT count(*) FROM tbl_name;

On the other hand, in a discussion of the COUNT() function, the same statement would be written like this:

mysql> select COUNT(*) from tbl_name;

If no particular emphasis is intended, all keywords are written uniformly in uppercase.

In syntax descriptions, square brackets (`[' and `]') are used to indicate optional words or clauses:

DROP TABLE [IF EXISTS] tbl_name

When a syntax element consists of a number of alternatives, the alternatives are separated by vertical bars (`|'). When one member from a set of choices may be chosen, the alternatives are listed within square brackets (`[' and `]'):

TRIM([[BOTH | LEADING | TRAILING] [remstr] FROM] str)

When one member from a set of choices must be chosen, the alternatives are listed within braces (`{' and `}'):

{DESCRIBE | DESC} tbl_name {col_name | wild}

1.4 History of MySQL

We once started out with the intention of using mSQL to connect to our tables using our own fast low-level (ISAM) routines. However, after some testing we came to the conclusion that mSQL was not fast enough nor flexible enough for our needs. This resulted in a new SQL interface to our database but with almost the same API interface as mSQL. This API was chosen to ease porting of third-party code.

The derivation of the name MySQL is not perfectly clear. Our base directory and a large number of our libraries and tools have had the prefix ``my'' for well over 10 years. However, Monty's daughter (some years younger) is also named My. Which of the two gave its name to MySQL is still a mystery, even for us.

1.5 Books About MySQL

While this manual is still the right place for up to date technical information, its primary goal is to contain everything there is to know about MySQL. It is sometimes nice to have a bound book to read in bed or while you travel. Here is a list of books about MySQL and related subjects (in English).

By purchasing a book through these hyperlinks provided herein, you are contributing to the development of MySQL.

MySQL

Available Barnes and Noble

Publisher New Riders

Author Paul DuBois

Pub Date 1st Edition December 1999

ISBN 0735709211

Pages 800

Price $49.99 US

Downloadable examples samp_db.tar.gz

Errata are available here

Foreword by Michael ``Monty'' Widenius, MySQL Moderator.

In MySQL, Paul DuBois provides you with a comprehensive guide to one of the most popular relational database systems. Paul has contributed to the online documentation for MySQL and is an active member of the MySQL community. The principal MySQL developer, Monty Widenius, and a network of his fellow developers reviewed the manuscript, and provided Paul with the kind of insight no one else could supply.

Instead of merely giving you a general overview of MySQL, Paul teaches you how to make the most of its capabilities. Through two sample database applications that run throughout the book, he gives you solutions to problems you're sure to face. He helps you integrate MySQL efficiently with third-party tools, such as PHP and Perl, enabling you to generate dynamic Web pages through database queries. He teaches you to write programs that access MySQL databases, and also provides a comprehensive set of references to column types, operators, functions, SQL syntax, MySQL programming, C API, Perl DBI, and PHP API. MySQL simply gives you the kind of information you won't find anywhere else.

If you use MySQL, this book provides you with:

An introduction to MySQL and SQL.
Coverage of MySQL's data types and how to use them.
Thorough treatment of how to write client programs in C.
A guide to using the Perl DBI and PHP APIs for developing command-line and Web-based applications.
Tips on administrative issues such as user accounts, backup, crash recovery, and security.
Help in choosing an ISP for MySQL access.
A comprehensive reference for MySQL's data types, operators, functions, and SQL statements and utilities.
Complete reference guides for MySQL's C API, the Perl DBI API, and PHP's MySQL-related functions.

MySQL & mSQL

Available Barnes and Noble

Publisher O'Reilly

Authors Randy Jay Yarger, George Reese & Tim King

Pub Date 1st Edition July 1999

ISBN 1-56592-434-7, Order Number: 4347

Pages 506

Price $34.95

This book teaches you how to use MySQL and mSQL, two popular and robust database products that support key subsets of SQL on both Linux and Unix systems. Anyone who knows basic C, Java, Perl, or Python can write a program to interact with a database, either as a stand-alone application or through a Web page. This book takes you through the whole process, from installation and configuration to programming interfaces and basic administration. Includes plenty of tutorial material.

Sams' Teach Yourself MySQL in 21 Days

Available Barnes and Noble

Publisher Sams

Authors Mark Maslakowski and Tony Butcher

Pub Date June 2000

ISBN 0672319144

Pages 650

Price $39.99

Sams' Teach Yourself MySQL in 21 Days is for intermediate Linux users who want to move into databases. A large share of the audience is Web developers who need a database to store large amounts of information that can be retrieved via the Web.

Sams' Teach Yourself MySQL in 21 Days is a practical, step-by-step tutorial. The reader will learn to design and employ this open source database technology into his or her Web site using practical, hands-on examples to follow.

E-Commerce Solutions with MySQL

Available Barnes and Noble

Publisher Prima Communications, Inc.

Authors N/A

Pub Date January 2000

ISBN 0761524452

Pages 500

Price $39.99

No description available.

MySQL and PHP from Scratch

Available Barnes and Noble

Publisher Que

Authors N/A

Pub Date September 2000

ISBN 0789724405

Pages 550

Price $34.99

This book puts together information on installing, setting up, and troubleshooting Apache, MySQL, PHP3, and IMP into one complete volume. You also learn how each piece is part of a whole by learning, step-by-step, how to create a web-based e-mail system. Learn to run the equivalent of Active Server Pages (ASP) using PHP3, set up an e-commerce site using a database and the Apache web server, and create a data entry system (such as sales, product quality tracking, customer preferences, etc) that no installation in the PC.

Professional MySQL Programming

Available Barnes and Noble

Publisher Wrox Press, Inc.

Authors N/A

Pub Date Late 2001

ISBN 1861005164

Pages 1000

Price $49.99

No description available.

Professional Linux Programming

Available Barnes and Noble

Publisher Wrox Press, Inc.

Authors N/A

Pub Date September 2000

ISBN 1861003013

Pages 1155

Price $47.99

In this follow-up to the best-selling Beginning Linux Programming, you will learn from the authors' real-world knowledge and experience of developing software for Linux; you'll be taken through the development of a sample 'DVD Store' application, with 'theme' chapters addressing different aspects of its implementation. Meanwhile, individual ``take-a-break'' chapters cover important topics that go beyond the bounds of the central theme. All focus on the practical aspects of programming, showing how crucial it is to choose the right tools for the job, use them as they should be used, and get things right first time.

PHP and MySQL Web Development

Available Barnes and Noble

Publisher Sams

Authors Luke Welling, Laura Thomson

Pub Date March 2001

ISBN 0672317842

Pages 700

Price $49.99

PHP and MySQL Web Development introduces you to the advantages of implementing both MySQL and PHP. These advantages are detailed through the provision of both statistics and several case studies. A practical web application is developed throughout the book, providing you with the tools necessary to implement a functional online database. Each function is developed separately, allowing you the choice to incorporate only those parts that you would like to implement. Programming concepts of the PHP language are highlighted, including functions which tie MySQL support into a PHP script and advanced topics regarding table manipulation.

Books recommended by the MySQL Developers

SQL-99 Complete, Really

Available Barnes and Noble

Publisher CMP Books

Authors Peter Gulutzan, Trudy Pelzer

Pub Date April 1999

ISBN 0879305681

Pages 1104

Price $55.96

This book contains complete descriptions of the new standards for syntax, data structures, and retrieval processes of SQL databases. As an example-based reference manual, it includes all of the CLI functions, information, schema tables, and status codes, as well as a working SQL database provided on the companion disk.

C, A reference manual

Available Barnes and Noble

Publisher Prentice Hall

Authors Samuel P. Harbison, Guy L. Steele

Pub Date September 1994

ISBN 0133262243

Pages 480

Price $35.99

A new and improved revision of the bestselling C language reference. This manual introduces the notion of "Clean C", writing C code that can be compiled as a C++ program, C programming style that emphasizes correctness, portability, maintainability, and incorporates the ISO C Amendment 1 (1994) which specifies new facilities for writing portable, international programs in C.

C++ for Real Programmers

Available Barnes and Noble

Publisher Academic Press, Incorporated

Authors Jeff Alger, Jim Keogh

Pub Date February 1998

ISBN 0120499428

Pages 388

Price $39.95

C++ For Real Programmers bridges the gap between C++ as described in beginner and intermediate-level books and C++ as it is practiced by experts. Numerous valuable techniques are described, organized into three simple themes: indirection, class hierarchies, and memory management. It also provides in-depth coverage of template creation, exception handling, pointers and optimization techniques. The focus of the book is on ANSI C++ and, as such, is compiler independent.

C++ For Real Programmers is a revision of Secrets of the C++ Masters and includes a new appendix comparing C++ with Java. The book comes with a 3.5" disk for Windows with source code.

Algorithms in C

Available Barnes and Noble

Publisher Addison Wesley Longman, Inc.

Authors Robert Sedgewick

Pub Date April 1990

ISBN 0201514257

Pages 648

Price $45.75

Algorithms in C describes a variety of algorithms in a number of areas of interest, including: sorting, searching, string-processing, and geometric, graph and mathematical algorithms. The book emphasizes fundamental techniques, providing readers with the tools to confidently implement, run, and debug useful algorithms.

Multithreaded Programming with Pthreads

Available Barnes and Noble

Publisher Prentice Hall

Authors Bil Lewis, Daniel J. Berg

Pub Date October 1997

ISBN 0136807291

Pages 432

Price $34.95

Based on the best-selling Threads Primer, Multithreaded Programming with Pthreads gives you a solid understanding of Posix threads: what they are, how they work, when to use them, and how to optimize them. It retains the clarity and humor of Threads Primer, but includes expanded comparisons to Win32 and OS/2 implementations. Code examples tested on all of the major UNIX platforms are featured along with detailed explanations of how and why they use threads.

Programming the PERL DBI: Database Programming with PERL

Available Barnes and Noble

Publisher O'Reilly & Associates, Incorporated

Authors Alligator Descartes, Tim Bunce

Pub Date February 2000

ISBN 1565926994

Pages 400

Price $27.96

Programming the Perl DBI is coauthored by Alligator Descartes, one of the most active members of the DBI community, and by Tim Bunce, the inventor of DBI. For the uninitiated, the book explains the architecture of DBI and shows you how to write DBI-based programs. For the experienced DBI dabbler, this book explains DBI's nuances and the peculiarities of each individual DBD.

The book includes:

An introduction to DBI and its design.
How to construct queries and bind parameters.
Working with database, driver, and statement handles.
Debugging techniques.
Coverage of each existing DBD.
A complete reference to DBI.

1.6 The Main Features of MySQL

The following list describes some of the important characteristics of MySQL:

Fully multi-threaded using kernel threads. This means it can easily use multiple CPUs if available.
C, C++, Eiffel, Java, Perl, PHP, Python and Tcl APIs. See section 24 MySQL APIs.
Works on many different platforms. See section 4.2 Operating Systems Supported by MySQL.
Many column types: signed/unsigned integers 1, 2, 3, 4, and 8 bytes long, FLOAT, DOUBLE, CHAR, VARCHAR, TEXT, BLOB, DATE, TIME, DATETIME, TIMESTAMP, YEAR, SET, and ENUM types. See section 7.3 Column Types.
Very fast joins using an optimized one-sweep multi-join.

Full operator and function support in the SELECT and WHERE parts of queries. For example:

mysql> SELECT CONCAT(first_name, " ", last_name) FROM tbl_name
           WHERE income/dependents > 10000 AND age > 30;

SQL functions are implemented through a highly optimized class library and should be as fast as possible! Usually there isn't any memory allocation at all after query initialization.
Full support for SQL GROUP BY and ORDER BY clauses. Support for group functions (COUNT(), COUNT(DISTINCT ...), AVG(), STD(), SUM(), MAX() and MIN()).
Support for LEFT OUTER JOIN and RIGHT OUTER JOIN with ANSI SQL and ODBC syntax.
You can mix tables from different databases in the same query (as of Version 3.22).
A privilege and password system that is very flexible and secure, and allows host-based verification. Passwords are secure because all password traffic is encrypted when you connect to a server.
ODBC (Open-DataBase-Connectivity) support for Win32 (with source). All ODBC 2.5 functions and many others. For example, you can use MS Access to connect to your MySQL server. See section 19 MySQL ODBC Support.
Very fast B-tree disk tables with index compression.
Up to 32 indexes per table are allowed. Each index may consist of 1 to 16 columns or parts of columns. The maximum index length is 500 bytes (this may be changed when compiling MySQL). An index may use a prefix of a CHAR or VARCHAR field.
Fixed-length and variable-length records.
In-memory hash tables which are used as temporary tables.
Handles large databases. We are using MySQL with some databases that contain 50,000,000 records and we know of users that uses MySQL with 60,000 tables and about 5,000,000,000 rows
All columns have default values. You can use INSERT to insert a subset of a table's columns; those columns that are not explicitly given values are set to their default values.
Uses GNU Automake, Autoconf, and Libtool for portability.
Written in C and C++. Tested with a broad range of different compilers.
A very fast thread-based memory allocation system.
No memory leaks. MySQL has been tested with Purify, a commercial memory leakage detector.
Includes myisamchk, a very fast utility for table checking, optimization, and repair. All of the functionality of myisamchk is also available through the SQL interface as well. See section 16 Maintaining a MySQL Installation.
Full support for several different character sets, including ISO-8859-1 (Latin1), big5, ujis, and more. For example, the Scandinavian characters `@ringaccent{a}', `@"a' and `@"o' are allowed in table and column names.
All data are saved in the chosen character set. All comparisons for normal string columns are case insensitive.
Sorting is done according to the chosen character set (the Swedish way by default). It is possible to change this when the MySQL server is started up. To see an example of very advanced sorting, look at the Czech sorting code. MySQL supports many different character sets that can be specified at compile and run time.
Aliases on tables and columns are allowed as in the SQL92 standard.
DELETE, INSERT, REPLACE, and UPDATE return the number of rows that were changed (affected). It is possible to return the number of rows matched instead by setting a flag when connecting to the server.
Function names do not clash with table or column names. For example, ABS is a valid column name. The only restriction is that for a function call, no spaces are allowed between the function name and the `(' that follows it. See section 7.40 Is MySQL Picky About Reserved Words?.
All MySQL programs can be invoked with the --help or -? options to obtain online assistance.
The server can provide error messages to clients in many languages. See section 10.1 What Languages Are Supported by MySQL?.
Clients may connect to the MySQL server using TCP/IP Sockets, Unix Sockets (Unixes), or Named Pipes (NT).
The MySQL-specific SHOW command can be used to retrieve information about databases, tables, and indexes. The EXPLAIN command can be used to determine how the optimizer resolves a query.

1.7 How Stable Is MySQL?

This section addresses the questions ``How stable is MySQL?'' and ``Can I depend on MySQL in this project?'' We will try to clarify some issues and to answer some of the more important questions that seem to concern many people. This section has been put together from information gathered from the mailing list (which is very active in reporting bugs).

At TcX, MySQL has worked without any problems in our projects since mid-1996. When MySQL was released to a wider public, we noticed that there were some pieces of ``untested code'' that were quickly found by the new users who made queries in a manner different than our own. Each new release has had fewer portability problems than the previous one (even though each has had many new features).

Each release of MySQL has been usable, and there have been problems only when users start to use code from the ``gray zones.'' Naturally, outside users don't know what the gray zones are; this section attempts to indicate those that are currently known. The descriptions deal with Version 3.23 of MySQL. All known and reported bugs are fixed in the latest version, with the exception of the bugs listed in the bugs section, which are things that are design-related. See section G Known errors and design deficiencies in MySQL.

MySQL is written in multiple layers and different independent modules. These modules are listed below with an indication of how well-tested each of them is:

The ISAM table handler -- Stable: This manages storage and retrieval of all data in MySQL Version 3.22 and earlier. In all MySQL releases there hasn't been a single (reported) bug in this code. The only known way to get a corrupted table is to kill the server in the middle of an update. Even that is unlikely to destroy any data beyond rescue, because all data are flushed to disk between each query. There hasn't been a single bug report about lost data because of bugs in MySQL.
The MyISAM table handler -- Gamma: This is new in MySQL Version 3.23. It's largely based on the ISAM table code but has a lot of new and very useful features.
The parser and lexical analyser -- Stable: There hasn't been a single reported bug in this system for a long time.
The C client code -- Stable: No known problems. In early Version 3.20 releases, there were some limitations in the send/receive buffer size. As of Version 3.21, the buffer size is now dynamic up to a default of 16M.
Standard client programs -- Stable: These include mysql, mysqladmin, mysqlshow, mysqldump, and mysqlimport.
Basic SQL -- Stable: The basic SQL function system and string classes and dynamic memory handling. Not a single reported bug in this system.
Query optimizer -- Stable
Range optimizer -- Stable
Join optimizer -- Stable
Locking -- Gamma: This is very system-dependent. On some systems there are big problems using standard OS locking (fcntl()). In these cases, you should run the MySQL daemon with the --skip-locking flag. Problems are known to occur on some Linux systems, and on SunOS when using NFS-mounted file systems.
Linux threads -- Stable: The major problem found has been with the fcntl() call, which is fixed by using the --skip-locking option to mysqld. Some people have reported lockup problems with Version 0.5. LinuxThreads will need to be recompiled if you plan to use 1000+ concurrent connections. Although it is possible to run that many connections with the default LinuxThreads (however, you will never go above 1021), the default stack spacing of 2 MB makes the application unstable, and we have been able to reproduce a coredump after creating 1021 idle connections. See section 4.12.5 Linux Notes (All Linux Versions).
Solaris 2.5+ pthreads -- Stable: We use this for all our production work.
MIT-pthreads (Other systems) -- Stable: There have been no reported bugs since Version 3.20.15 and no known bugs since Version 3.20.16. On some systems, there is a ``misfeature'' where some operations are quite slow (a 1/20 second sleep is done between each query). Of course, MIT-pthreads may slow down everything a bit, but index-based SELECT statements are usually done in one time frame so there shouldn't be a mutex locking/thread juggling.
Other thread implementions -- Beta - Gamma: The ports to other systems are still very new and may have bugs, possibly in MySQL, but most often in the thread implementation itself.
LOAD DATA ..., INSERT ... SELECT -- Stable: Some people thought they had found bugs here, but these usually have turned out to be misunderstandings. Please check the manual before reporting problems!
ALTER TABLE -- Stable: Small changes in Version 3.22.12.
DBD -- Stable: Now maintained by Jochen Wiedmann (wiedmann@neckar-alb.de). Thanks!
mysqlaccess -- Stable: Written and maintained by Yves Carlier (Yves.Carlier@rug.ac.be). Thanks!
GRANT -- Stable: Big changes made in MySQL Version 3.22.12.
MyODBC (uses ODBC SDK 2.5) -- Gamma: It seems to work well with some programs.
Replication -- Beta / Gamma: We are still working on replication, so don't expect this to be rock solid yet. On the other hand, some MySQL users are already using this with good results.
BDB Tables -- Beta: The Berkeley DB code is very stable, but we are still improving the interface between MySQL and BDB tables, so it will take some time before this is as tested as the other table types.
Innodb Tables -- Alpha: This is a very recent addition to MySQL and is not very tested yet.
Automatic recovery of MyISAM tables - Beta: This only affects the new code that checks if the table was closed properly on open and executes an automatic check/repair of the table if it wasn't.
MERGE tables -- Beta / Gamma: The usage of keys on MERGE tables is still not that tested. The other part of the MERGE code is quite well tested.
FULLTEXT -- Beta: Text search seems to work, but is still not widely used.

MySQL AB provides e-mail support for paying customers, but the MySQL mailing list usually provides answers to common questions. Bugs are usually fixed right away with a patch; for serious bugs, there is almost always a new release.

1.8 Year 2000 Compliance

MySQL itself has no problems with Year 2000 (Y2K) compliance:

MySQL uses Unix time functions and has no problems with dates until 2069; all 2-digit years are regarded to be in the range 1970 to 2069, which means that if you store 01 in a year column, MySQL treats it as 2001.
All MySQL date functions are stored in one file `sql/time.cc' and coded very carefully to be year 2000-safe.
In MySQL Version 3.22 and later, the new YEAR column type can store years 0 and 1901 to 2155 in 1 byte and display them using 2 or 4 digits.

You may run into problems with applications that use MySQL in a way that is not Y2K-safe. For example, many old applications store or manipulate years using 2-digit values (which are ambiguous) rather than 4-digit values. This problem may be compounded by applications that use values such as 00 or 99 as ``missing'' value indicators.

Unfortunately, these problems may be difficult to fix, because different applications may be written by different programmers, each of whom may use a different set of conventions and date-handling functions.

Here is a simple demonstration illustrating that MySQL doesn't have any problems with dates until the year 2030:

mysql> DROP TABLE IF EXISTS y2k;
Query OK, 0 rows affected (0.01 sec)

mysql> CREATE TABLE y2k (date date, date_time datetime, time_stamp timestamp);
Query OK, 0 rows affected (0.00 sec)

mysql> INSERT INTO y2k VALUES 
    -> ("1998-12-31","1998-12-31 23:59:59",19981231235959),
    -> ("1999-01-01","1999-01-01 00:00:00",19990101000000),
    -> ("1999-09-09","1999-09-09 23:59:59",19990909235959),
    -> ("2000-01-01","2000-01-01 00:00:00",20000101000000),
    -> ("2000-02-28","2000-02-28 00:00:00",20000228000000),
    -> ("2000-02-29","2000-02-29 00:00:00",20000229000000),
    -> ("2000-03-01","2000-03-01 00:00:00",20000301000000),
    -> ("2000-12-31","2000-12-31 23:59:59",20001231235959),
    -> ("2001-01-01","2001-01-01 00:00:00",20010101000000),
    -> ("2004-12-31","2004-12-31 23:59:59",20041231235959),
    -> ("2005-01-01","2005-01-01 00:00:00",20050101000000),
    -> ("2030-01-01","2030-01-01 00:00:00",20300101000000),
    -> ("2050-01-01","2050-01-01 00:00:00",20500101000000);
Query OK, 13 rows affected (0.01 sec)
Records: 13  Duplicates: 0  Warnings: 0

mysql> SELECT * FROM y2k;
+------------+---------------------+----------------+
| date       | date_time           | time_stamp     |
+------------+---------------------+----------------+
| 1998-12-31 | 1998-12-31 23:59:59 | 19981231235959 |
| 1999-01-01 | 1999-01-01 00:00:00 | 19990101000000 |
| 1999-09-09 | 1999-09-09 23:59:59 | 19990909235959 |
| 2000-01-01 | 2000-01-01 00:00:00 | 20000101000000 |
| 2000-02-28 | 2000-02-28 00:00:00 | 20000228000000 |
| 2000-02-29 | 2000-02-29 00:00:00 | 20000229000000 |
| 2000-03-01 | 2000-03-01 00:00:00 | 20000301000000 |
| 2000-12-31 | 2000-12-31 23:59:59 | 20001231235959 |
| 2001-01-01 | 2001-01-01 00:00:00 | 20010101000000 |
| 2004-12-31 | 2004-12-31 23:59:59 | 20041231235959 |
| 2005-01-01 | 2005-01-01 00:00:00 | 20050101000000 |
| 2030-01-01 | 2030-01-01 00:00:00 | 20300101000000 |
| 2050-01-01 | 2050-01-01 00:00:00 | 00000000000000 |
+------------+---------------------+----------------+
13 rows in set (0.00 sec)

This shows that the DATE and DATETIME types will not give any problems with future dates (they handle dates until the year 9999).

The TIMESTAMP type, which is used to store the current time, has a range up to only 2030-01-01. TIMESTAMP has a range of 1970 to 2030 on 32-bit machines (signed value). On 64-bit machines it handles times up to 2106 (unsigned value).

Even though MySQL is Y2K-compliant, it is your responsibility to provide unambiguous input. See section 7.3.3.1 Y2K Issues and Date Types for MySQL's rules for dealing with ambiguous date input data (data containing 2-digit year values).

1.9 General SQL Information and Tutorials

The following book has been recommended by several people on the MySQL mailing list:

Judith S. Bowman, Sandra L. Emerson and Marcy Darnovsky
The Practical SQL Handbook: Using Structured Query Language
Second Edition
Addison-Wesley
ISBN 0-201-62623-3
http://www.awl.com

The following book has also received some recommendations by MySQL users:

Martin Gruber
Understanding SQL
ISBN 0-89588-644-8
Publisher Sybex 510 523 8233
Alameda, CA USA

A SQL tutorial is available on the net at http://w3.one.net/~jhoffman/sqltut.htm

1.10 Useful MySQL-related Links

Apart from the following links, you can find and download a lot of MySQL programs, tools and APIs from the Contrib directory.

MySQL

1.10.1 Tutorials and Manuals

MySQL Myths Debunked: MySQL used in the real world.
http://www.4t2.com/mysql: Information about the German MySQL mailing list.
http://www2.rent-a-database.de/mysql/: MySQL manual in German.
http://www.bitmover.com:8888//home/bk/mysql: Web access to the MySQL BitKeeper repository.
http://www.analysisandsolutions.com/code/mybasic.htm: Beginners MySQL Tutorial on how to install and set up MySQL on a Windows machine.
http://www.devshed.com/Server_Side/MySQL/: A lot of MySQL tutorials.
http://mysql.hitstar.com/: MySQL manual in Chinese.
http://www.linuxplanet.com/linuxplanet/tutorials/1046/1/: Setting Up a MySQL-based Web site.
http://www.hotwired.com/webmonkey/backend/tutorials/tutorial1.html: MySQL-Perl tutorial.
http://www.iserver.com/support/contrib/perl5/modules.html: Installing new Perl modules that require locally installed modules.
http://www.hotwired.com/webmonkey/databases/tutorials/tutorial4.html: PHP/MySQL Tutorial.
http://www.useractive.com/: Hands on tutorial for MySQL.

1.10.2 Porting MySQL/Using MySQL on Different Systems

http://xclave.macnn.com/MySQL/: The Mac OS Xclave. Running MySQL on Mac OS X.
http://www.prnet.de/RegEx/mysql.html: MySQL for Mac OS X Server.
http://www.latencyzero.com/macosx/mysql.html: Building MySQL for Mac OS X.
http://www.essencesw.com/Software/mysqllib.html: New Client libraries for the Mac OS Classic (Macintosh).
http://www.lilback.com/macsql/: Client libraries for Mac OS Classic (Macintosh).

1.10.3 Perl-related Links

http://dbimysql.photoflux.com/: Perl DBI with MySQL FAQ.

1.10.4 MySQL Discussion Forums

http://www.weberdev.com/: Examples using MySQL; (check Top 20)
http://futurerealm.com/forum/futureforum.htm: FutureForum Web Discussion Software.

1.10.5 Commercial Applications that Support MySQL

http://www.supportwizard.com/: SupportWizard; Interactive helpdesk on the Web (This product includes a licensed copy of MySQL.)
http://www.sonork.com/: Sonork, Instant Messenger that is not only Internet oriented. It's focused on private networks and on small to medium companies. Client is free, server is free for up to 5 seats.
http://www.stweb.org/: StWeb - Stratos Web and Application server - An easy-to-use, cross platform, Internet/Intranet development and deployment system for development of web-enabled applications. The standard version of StWeb has a native interface to MySQL database.
http://www.rightnowtech.com/: Right Now Web; Web automation for customer service.
http://www.icaap.org/Bazaar/: Bazaar; Interactive Discussion Forums with Web interface.
http://www.phonesweep.com/: PhoneSweepT is the world's first commercial Telephone Scanner. Many break-ins in recent years have come not through the Internet, but through unauthorized dial-up modems. PhoneSweep lets you find these modems by repeatedly placing phone calls to every phone number that your organization controls. PhoneSweep has a built-in expert system that can recognize more than 250 different kinds of remote-access programs, including Carbon Copy(TM), pcANYWHERE(TM), and Windows NT RAS. All information is stored in the SQL database. It then generates a comprehensive report detailing which services were discovered on which dial-up numbers in your organization.

1.10.6 SQL Clients and Report Writers

urSQL: SQL Editor and Query Utility. Custom syntax highlighting, editable results grid, exportable result-sets, basic MySQL admin functions, Etc.. For windows.
MySQL Data Manager: MySQL Data Manager * is platform independent web client (written in perl) for MySQL server over TCP/IP.
http://ksql.sourceforge.net/: KDE MySQL client.
http://www.ecker-software.de: A Windows GUI client by David Ecker.
http://www.icaap.org/software/kiosk/: Kiosk; a MySQL client for database management. Written in Perl. Will be a part of Bazaar.
http://www.casestudio.com/: Db design tool that supports MySQL 3.23.
http://home.skif.net/~voland/zeos/eng/index.html: Zeos - A client that supports MySQL, Interbase and PostgreSQL.
http://www.geocities.com/SiliconValley/Ridge/4280/GenericReportWriter/grwhome.html: A free report writer in Java
http://www.javaframework.de: MySQLExport - Export of MySQL create statements and data in a lot of different formats (SQL, HTML, CVS, text, ZIP, GZIP...)
http://dlabs.4t2.com: M2D, a MySQL Administration client for Windows. M2D supports administration of MySQL databases, creation of new databasess and tables, editing, and more.
http://www.scibit.com/Products/Software/Utils/Mascon.asp: Mascon is a powerful Win32 GUI for administering MySQL databases.
http://www.rtlabs.com/: MacSQL Monitor. GUI for MySQL, ODBC, and JDBC databases for the Mac OS.

1.10.7 Distributions that Include MySQL

http://www.suse.com/: SuSE Linux (6.1 and above)
http://www.redhat.com/: RedHat Linux (7.0 and above)
http://distro.conectiva.com.br: Conectiva Linux (4.0 and above)

1.10.8 Web Development Tools that Support MySQL

http://www.php.net/: PHP: A server-side HTML-embedded scripting language.
http://www.midgard-project.org: The Midgard Application Server; a powerful Web development environment based on MySQL and PHP.
http://www.smartworker.org: SmartWorker is a platform for Web application development.
http://xsp.lentus.se/: XSP: e(X)tendible (S)erver (P)ages and is a HTML embedded tag language written in Java (previously known as XTAGS.)
http://www.dbServ.de/: dbServ is an extension to a web server to integrate database output into your HTML code. You may use any HTML function in your output. Only the client will stop you. It works as standalone server or as Java servlet.
http://www.chilisoft.com/: Platform independent ASP from Chili!Soft
http://www.voicenet.com/~zellert/tjFM: A JDBC driver for MySQL.
http://www.wernhart.priv.at/php/: MySQL + PHP demos.
http://www.dbwww.com/: ForwardSQL: HTML interface to manipulate MySQL databases.
http://www.daa.com.au/~james/www-sql/: WWW-SQL: Display database information.
http://www.minivend.com/minivend/: Minivend: A Web shopping cart.
http://www.heitml.com/: HeiTML: A server-side extension of HTML and a 4GL language at the same time.
http://www.metahtml.com/: Metahtml: A Dynamic Programming Language for WWW Applications.
http://www.binevolve.com/: VelocityGen for Perl and Tcl.
http://hawkeye.net/: Hawkeye Internet Server Suite.
http://www.fastflow.com/: Network Database Connection For Linux
http://www.wdbi.net/: WDBI: Web browser as a universal front end to databases which supports MySQL well.
http://www.webgroove.com/: WebGroove Script: HTML compiler and server-side scripting language.
http://www.ihtml.com/: A server-side Web site scripting language.
ftp://ftp.igc.apc.org/pub/myodbc/README: How to use MySQL with ColdFusion on Solaris.
http://calistra.com/MySQL/: Calistra's ODBC MySQL Administrator.
http://www.webmerger.com: Webmerger - This CGI tool interprets files and generates dynamic output based on a set of simple tags. Ready-to-run drivers for MySQL and PostgreSQL through ODBC.
http://phpclub.net/: PHPclub - Tips and tricks for PHP.
http://www.penguinservices.com/scripts: MySQL and Perl Scripts.
http://www.widgetchuck.com: The Widgetchuck; Web Site Tools and Gadgets
http://www.adcycle.com/: AdCycle - advertising management software.
http://sourceforge.net/projects/pwpage/: pwPage - provides an extremely fast and simple approach to the creation of database forms. That is, if a database table exists and an HTML page has been constructed using a few simple guidelines, pwPage can be immediately used for table data selections, insertions, updates, deletions and selectable table content reviewing.
http://www.omnis-software.com/products/studio/studio.html: OMNIS Studio is a rapid application development (RAD) tool.
http://www.webplus.com: talentsoft Web+ 4.6 - a powerful and comprehensive development language for use in creating web-based client/server applications without writing complicated, low-level, and time-consuming CGI programs.

1.10.9 Database Design Tools with MySQL Support

http://www.mysql.com/documentation/dezign/: "DeZign for databases" is a database development tool that uses an entity relationship diagram (ERD).

1.10.10 Web Servers with MySQL Tools

http://bourbon.netvision.net.il/mysql/mod_auth_mysql/: An Apache authentication module.
http://www.roxen.com/: The Roxen Challenger Web server.

1.10.11 Extensions for Other Programs

http://www.seawood.org/msql_bind/: MySQL support for BIND (The Internet Domain Name Server).
http://www.inet-interactive.com/sendmail/: MySQL support for Sendmail and Procmail.

1.10.12 Using MySQL with Other Programs

http://www.iserver.com/support/addonhelp/database/mysql/msaccess.html: Using MySQL with Access.
http://www.iserver.com/support/contrib/perl5/modules.html: Installing new Perl modules that require locally installed modules.

1.10.13 ODBC-related Links

http://www.iodbc.org/: Popular iODBC Driver Manager (libiodbc) now available as Open Source.
http://users.ids.net/~bjepson/freeODBC/: The FreeODBC Pages.
http:/http://genix.net/unixODBC/: The unixODBC Project goals are to develop and promote unixODBC to be the definitive standard for ODBC on the Linux platform. This is to include GUI support for KDE.
http://www.sw-soft.com/products/BtrieveODBC/: A MySQL-based ODBC driver for Btrieve.

1.10.14 API-related Links

http://www.jppp.com/: Partially implemented TDataset-compatible components for MySQL.
http://www.riverstyx.net/qpopmysql/: qpopmysql - A patch to allow POP3 authentication from a MySQL database. There's also a link to Paul Khavkine's patch for Procmail to allow any MTA to deliver to users in a MySQL database.
http://www.pbc.ottawa.on.ca: Visual Basic class generator for Active X.
http://www.essencesw.com/Software/mysqllib.html: New Client libraries for the Mac OS Classic (Macintosh).
http://www.lilback.com/macsql/: Client libraries for the Macintosh.
http://www.essencesw.com/Plugins/mysqlplug.html: Plugin for REALbasic (for Macintosh)
http://www.iis.ee.ethz.ch/~neeri/macintosh/gusi-qa.html: A library that emulates BSD sockets and pthreads on Macintosh. This can be used if you want to compile the MySQL client library on Mac. It could probably even be sued to port MySQL to Macintosh, but we don't know of anyone that has tried that.
http://www.dedecker.net/jessie/scmdb/: SCMDB - an add-on for SCM that ports the mysql C library to scheme (SCM). With this library scheme developers can make connections to a mySQL database and use embedded SQL in their programs.

1.10.15 Other MySQL-related Links

SAT: The Small Application Toolkit (SAT) is a collection of utilities intended to simplify the development of small, multi-user, GUI based applications in a (Microsoft -or- X) Windows Client / Unix Server environment.
http://www.wix.com/mysql-hosting/: Registry of Web providers who support MySQL.
http://www.softagency.co.jp/mysql/index.en.phtml: Links about using MySQL in Japan/Asia.
http://abattoir.cc.ndsu.nodak.edu/~nem/mysql/udf/: MySQL UDF Registry.
http://www.open.com.au/products.html: Commercial Web defect tracking system.
http://www.stonekeep.com/pts/: PTS: Project Tracking System.
http://tomato.nvgc.vt.edu/~hroberts/mot: Job and software tracking system.
http://www.cynergi.net/non-secure/exportsql/: ExportSQL: A script to export data from Access95+.
http://SAL.KachinaTech.COM/H/1/MYSQL.html: SAL (Scientific Applications on Linux) MySQL entry.
http://www.infotech-nj.com/itech/index.shtml: A consulting company which mentions MySQL in the right company.
http://www.pmpcs.com/: PMP Computer Solutions. Database developers using MySQL and mSQL.
http://www.aewa.org/: Airborne Early Warning Association.
http://www.dedserius.com/y2kmatrix/: Y2K tester.

1.10.16 SQL and Database Interfaces

http://java.sun.com/products/jdbc/: The JDBC database access API.
http://www.gagme.com/mysql: Patch for mSQL Tcl.
http://www.amsoft.ru/easysql/: EasySQL: An ODBC-like driver manager.
http://www.lightlink.com/hessling/rexxsql.html: A REXX interface to SQL databases.
http://www.mytcl.cx/: Tcl interface based on tcl-sql with many bugfixes.
http://www.binevolve.com/~tdarugar/tcl-sql/: Tcl interface.
http://www.contrib.andrew.cmu.edu/~shadow/sql.html: SQL Reference Page with a lot of interesting links.

1.10.17 Examples of MySQL Use

http://www.little6.com/about/linux/: Little6 Inc., An online contract and job finding site that is powered by MySQL, PHP3, and Linux.
http://www.delec.com/is/products/prep/examples/BookShelf/index.html: DELECis - A tool that makes it very easy to create an automatically generated table documentation. They have used MySQL as an example.
http://www.worldrecords.com: World Records - A search engine for information about music that uses MySQL and PHP.
http://www.webtechniques.com/archives/1998/01/note/: A Contact Database using MySQL and PHP.
http://modems.rosenet.net/mysql/: Web based interface and Community Calendar with PHP.
http://www.odbsoft.com/cook/sources.htm: Perl package to generate html from a SQL table structure and for generating SQL statements from an html form.
http://www.gusnet.cx/proj/telsql/: Basic telephone database using DBI/DBD.
http://tecfa.unige.ch/guides/java/staf2x/ex/jdbc/coffee-break: JDBC examples by Daniel K. Schneider.
http://www.spade.com/linux/howto/PostgreSQL-HOWTO-41.html: SQL BNF
http://www.ooc.com/: Object Oriented Concepts Inc; CORBA applications with examples in source.
http://www.pbc.ottawa.on.ca/: DBWiz; Includes an example of how to manage cursors in VB.
http://keilor.cs.umass.edu/pluribus/: Pluribus is a free search engine that learns to improve the quality of its results over time. Pluribus works by recording which pages a user prefers among those returned for a query. A user votes for a page by selecting it; Pluribus then uses that knowledge to improve the quality of the results when someone else submits the same (or similar) query. Uses PHP and MySQL.
http://www.stopbit.com/: Stopbit - A technology news site using MySQL and PHP.
http://www.jokes2000.com/scripts/: Example scripts at Jokes2000.
http://www.linuxsupportline.com/~kalendar/: KDE based calendar manager - The calendar manager has both single user (file based) and multi-user (MySQL database) support.
http://tim.desert.net/~tim/imger/: Example of storing/retrieving images with MySQL and CGI.
http://www.penguinservices.com/scripts: Online shopping cart system.
http://www.city-gallery.com/album/: Old Photo Album - The album is a collaborative popular history of photography project that generates all pages from data stored in a MySQL database. Pages are dynamically generated through a php3 interface to the database content. Users contribute images and descriptions. Contributed images are stored on the web server to avoid storing them in the database as BLOBs. All other information is stored on the shared MySQL server.

1.10.18 General Database Links

http://www.pcslink.com/~ej/dbweb.html: Database Jump Site
http://black.hole-in-the.net/guy/webdb/: Homepage of the webdb-l (Web Databases) mailing list.
http://www.symbolstone.org/technology/perl/DBI/index.html: Perl DBI/DBD modules homepage.
http://www.student.uni-koeln.de/cygwin/: Cygwin tools. Unix on top of Windows.
http://dbasecentral.com/: dbasecentral.com; Development and distribution of powerful and easy-to-use database applications and systems.
http://www.tek-tips.com/: Tek-Tips Forums are 800+ independent peer-to-peer non-commercial support forums for Computer Professionals. Features include automatic e-mail notification of responses, a links library, and member confidentiality guaranteed.
http://www.public.asu.edu/~peterjn/btree/: B-Trees: Balanced Tree Data Structures.
http://www.fit.qut.edu.au/~maire/baobab/lecture/sld001.htm: A lecture about B-Trees.

There are also many Web pages that use MySQL. See section B Some MySQL Users. Send any additions to this list to webmaster@mysql.com. We now require that you show a MySQL logo somewhere if you wish your site to be added. It is okay to have it on a ``used tools'' page or something similar.

2 MySQL Mailing Lists

This chapter introduces you to the MySQL mailing lists, and gives some guidelines as to how to use them.

2.1 The MySQL Mailing Lists

To subscribe to the main MySQL mailing list, send a message to the electronic mail address mysql-subscribe@lists.mysql.com.

To unsubscribe from the main MySQL mailing list, send a message to the electronic mail address mysql-unsubscribe@lists.mysql.com.

Only the address to which you send your messages is significant. The subject line and the body of the message are ignored.

If your reply address is not valid, you can specify your address explicitly. Adding a hyphen to the subscribe or unsubscribe command word, followed by your address with the `@' character in your address replaced by a `='. For example, to subscribe your_name@host.domain, send a message to mysql-subscribe-your_name=host.domain@lists.mysql.com.

Mail to mysql-subscribe@lists.mysql.com or mysql-unsubscribe@lists.mysql.com is handled automatically by the ezmlm mailing list processor. Information about ezmlm is available at The ezmlm Website.

To post a message to the list itself, send your message to mysql@lists.mysql.com. However, please do not send mail about subscribing or unsubscribing to mysql@lists.mysql.com, because any mail sent to that address is distributed automatically to thousands of other users.

Your local site may have many subscribers to mysql@lists.mysql.com. If so, it may have a local mailing list, so that messages sent from lists.mysql.com to your site are propagated to the local list. In such cases, please contact your system administrator to be added to or dropped from the local MySQL list.

The following MySQL mailing lists exist:

, announce: This is for announcement of new versions of MySQL and related programs. This is a low volume list all MySQL users should subscribe to.
, mysql: The main list for general MySQL discussion. Please note that some topics are better discussed on the more-specialized lists. If you post to the wrong list, you may not get an answer!
, mysql-digest: The mysql list in digest form. That means you get all individual messages, sent as one large mail message once a day.
, bugs: On this list you should only post a full, repeatable bug report using the mysqlbug script (if you are running on Windows, you should include a description of the operating system and the MySQL version). Preferably, you should test the problem using the latest stable or development version of MySQL before posting! Anyone should be able to repeat the bug by just using mysql test < script on the included test case. All bugs posted on this list will be corrected or documented in the next MySQL release! If there are only small code changes involved, we will also post a patch that fixes the problem.
, bugs-digest: The bugs list in digest form.
, developer: This list has been depreciated in favor of the , internals list (below).
, developer-digest: This list has been deprecated in favor of the , internals-digest list (below).
, internals: A list for people who work on the MySQL code. On this list one can also discuss MySQL development and post patches.
, internals-digest: A digest version of the , internals list.
, java: Discussion about MySQL and Java. Mostly about the JDBC drivers.
, java-digest: A digest version of the java list.
, win32: All things concerning MySQL on Microsoft operating systems such as Win95, Win98, NT, and Win2000.
, win32-digest: A digest version of the win32 list.
, myodbc: All things about connecting to MySQL with ODBC.
, myodbc-digest: A digest version of the myodbc list.
, plusplus: All things concerning programming with the C++ API to MySQL.
, plusplus-digest: A digest version of the plusplus list.
, msql-mysql-modules: A list about the Perl support in MySQL.
, msql-mysql-modules-digest: A digest version of the msql-mysql-modules list.

You subscribe or unsubscribe to all lists in the same way as described above. In your subscribe or unsubscribe message, just put the appropriate mailing list name rather than mysql. For example, to subscribe to or unsubscribe from the myodbc list, send a message to myodbc-subscribe@lists.mysql.com or myodbc-unsubscribe@lists.mysql.com.

There is also a german mailing list. You can find information about this at: http://www.4t2.com/mysql.

2.2 Asking Questions or Reporting Bugs

Before posting a bug report or question, please do the following:

Start by searching the MySQL online manual at:
http://www.mysql.com/documentation/manual.php
We try to keep the manual up to date by updating it frequently with solutions to newly found problems!
Search the MySQL mailing list archives:
http://www.mysql.com/documentation/
You can also use http://www.mysql.com/search.html to search all the Web pages (including the manual) that are located at http://www.mysql.com/.

If you can't find an answer in the manual or the archives, check with your local MySQL expert. If you still can't find an answer to your question, go ahead and read the next section about how to send mail to mysql@lists.mysql.com.

2.3 How to Report Bugs or Problems

Writing a good bug report takes patience, but doing it right the first time saves time for us and for you. A good bug report containing a full test case for the bug will make it very likely that we will fix it in the next release. This section will help you write your report correctly so that you don't waste your time doing things that may not help us much or at all.

We encourage everyone to use the mysqlbug script to generate a bug report (or a report about any problem), if possible. mysqlbug can be found in the `scripts' directory in the source distribution, or, for a binary distribution, in the `bin' directory under your MySQL installation directory. If you are unable to use mysqlbug, you should still include all the necessary information listed in this section.

The mysqlbug script helps you generate a report by determining much of the following information automatically, but if something important is missing, please include it with your message! Please read this section carefully and make sure that all the information described here is included in your report.

The normal place to report bugs and problems is mysql@lists.mysql.com. If you can make a test case that clearly demonstrates the bug, you should post it to the bugs@lists.mysql.com list. Note that on this list you should only post a full, repeatable bug report using the mysqlbug script. If you are running on Windows, you should include a description of the operating system and the MySQL version. Preferably, you should test the problem using the latest stable or development version of MySQL before posting! Anyone should be able to repeat the bug by just using ``mysql test < script'' on the included test case or run the shell or perl script that is included in the bug report. All bugs posted on the bugs list will be corrected or documented in the next MySQL release! If there are only small code changes involved to correct this problem, we will also post a patch that fixes the problem.

Remember that it is possible to respond to a message containing too much information, but not to one containing too little. Often people omit facts because they think they know the cause of a problem and assume that some details don't matter. A good principle is: if you are in doubt about stating something, state it! It is a thousand times faster and less troublesome to write a couple of lines more in your report than to be forced to ask again and wait for the answer because you didn't include enough information the first time.

The most common errors are that people don't indicate the version number of the MySQL distribution they are using, or don't indicate what platform they have MySQL installed on (including the platform version number). This is highly relevant information, and in 99 cases out of 100 the bug report is useless without it! Very often we get questions like, ``Why doesn't this work for me?'' then we find that the feature requested wasn't implemented in that MySQL version, or that a bug described in a report has been fixed already in newer MySQL versions. Sometimes the error is platform dependent; in such cases, it is next to impossible to fix anything without knowing the operating system and the version number of the platform.

Remember also to provide information about your compiler, if it is related to the problem. Often people find bugs in compilers and think the problem is MySQL-related. Most compilers are under development all the time and become better version by version. To determine whether or not your problem depends on your compiler, we need to know what compiler is used. Note that every compiling problem should be regarded as a bug report and reported accordingly.

It is most helpful when a good description of the problem is included in the bug report. That is, a good example of all the things you did that led to the problem and the problem itself exactly described. The best reports are those that include a full example showing how to reproduce the bug or problem. See section I.1.5 Making a test case when you experience table corruption.

If a program produces an error message, it is very important to include the message in your report! If we try to search for something from the archives using programs, it is better that the error message reported exactly matches the one that the program produces. (Even the case should be observed!) You should never try to remember what the error message was; instead, copy and paste the entire message into your report!

If you have a problem with MyODBC, you should try to genereate a MyODBC trace file. See section 19.7 Reporting Problems with MyODBC.

Please remember that many of the people who will read your report will do so using an 80-column display. When generating reports or examples using the mysql command line tool, you should therefore use the --vertical option (or the \G statement terminator) for output that would exceed the available width for such a display (for example, with the EXPLAIN SELECT statement; see the example below).

Please include the following information in your report:

The version number of the MySQL distribution you are using (for example, MySQL Version 3.22.22). You can find out which version you are running by executing mysqladmin version. mysqladmin can be found in the `bin' directory under your MySQL installation directory.
The manufacturer and model of the machine you are working on.
The operating system name and version. For most operating systems, you can get this information by executing the Unix command uname -a.
Sometimes the amount of memory (real and virtual) is relevant. If in doubt, include these values.
If you are using a source distribution of MySQL, the name and version number of the compiler used is needed. If you have a binary distribution, the distribution name is needed.
If the problem occurs during compilation, include the exact error message(s) and also a few lines of context around the offending code in the file where the error occurred.
If mysqld died, you should also report the query that crashed mysqld. You can usually find this out by running mysqld with logging enabled. See section I.1.4 Using log files to find cause of errors in mysqld.
If any database table is related to the problem, include the output from mysqldump --no-data db_name tbl_name1 tbl_name2 .... This is very easy to do and is a powerful way to get information about any table in a database that will help us create a situation matching the one you have.
For speed-related bugs or problems with SELECT statements, you should always include the output of EXPLAIN SELECT ..., and at least the number of rows that the SELECT statement produces. The more information you give about your situation, the more likely it is that someone can help you! For example, the following is an example of a very good bug report (it should of course be posted with the mysqlbug script): Example run using the mysql command line tool (note the use of the \G statement terminator for statements whose output width would otherwise exceed that of an 80-column display device):
```
mysql> SHOW VARIABLES;
mysql> SHOW COLUMNS FROM ...\G
       <output from SHOW COLUMNS>
mysql> EXPLAIN SELECT ...\G
       <output from EXPLAIN>
mysql> FLUSH STATUS;
mysql> SELECT ...;
       <A short version of the output from SELECT,
       including the time taken to run the query>
mysql> SHOW STATUS;
       <output from SHOW STATUS>
```
If a bug or problem occurs while running mysqld, try to provide an input script that will reproduce the anomaly. This script should include any necessary source files. The more closely the script can reproduce your situation, the better. If you can make a repeatable test case, you should post this to bugs@lists.mysql.com for a high priority treatment! If you can't provide a script, you should at least include the output from mysqladmin variables extended-status processlist in your mail to provide some information of how your system is performing!
If you can't produce a test case in a few rows, or if the test table is too big to be mailed to the mailing list (more than 10 rows), you should dump your tables using mysqldump and create a `README' file that describes your problem. Create a compressed archive of your files using tar and gzip or zip, and use ftp to transfer the archive to ftp://support.mysql.com/pub/mysql/secret/. Then send a short description of the problem to bugs@lists.mysql.com.
If you think that MySQL produces a strange result from a query, include not only the result, but also your opinion of what the result should be, and an account describing the basis for your opinion.
When giving an example of the problem, it's better to use the variable names, table names, etc., that exist in your actual situation than to come up with new names. The problem could be related to the name of a variable or table! These cases are rare, perhaps, but it is better to be safe than sorry. After all, it should be easier for you to provide an example that uses your actual situation, and it is by all means better for us. In case you have data you don't want to show to others, you can use ftp to transfer it to ftp://support.mysql.com/pub/mysql/secret/. If the data are really top secret and you don't want to show them even to us, then go ahead and provide an example using other names, but please regard this as the last choice.
Include all the options given to the relevant programs, if possible. For example, indicate the options that you use when you start the mysqld daemon and that you use to run any MySQL client programs. The options to programs like mysqld and mysql, and to the configure script, are often keys to answers and are very relevant! It is never a bad idea to include them anyway! If you use any modules, such as Perl or PHP, please include the version number(s) of those as well.
If your question is related to the privilege system, please include the output of mysqlaccess, the output of mysqladmin reload, and all the error messages you get when trying to connect! When you test your privileges, you should first run mysqlaccess. After this, execute mysqladmin reload version and try to connect with the program that gives you trouble. mysqlaccess can be found in the `bin' directory under your MySQL installation directory.
If you have a patch for a bug, that is good, but don't assume the patch is all we need, or that we will use it, if you don't provide some necessary information, such as test cases showing the bug that your patch fixes. We might find problems with your patch or we might not understand it at all; if so, we can't use it. If we can't verify exactly what the patch is meant for, we won't use it. Test cases will help us here. Show that the patch will handle all the situations that may occur. If we find a borderline case (even a rare one) where the patch won't work, it may be useless.
Guesses about what the bug is, why it occurs, or what it depends on, are usually wrong. Even the MySQL team can't guess such things without first using a debugger to determine the real cause of a bug.
Indicate in your mail message that you have checked the reference manual and mail archive so others know that you have tried to solve the problem yourself.
If you get a parse error, please check your syntax closely! If you can't find something wrong with it, it's extremely likely that your current version of MySQL doesn't support the query you are using. If you are using the current version and the manual at http://www.mysql.com/documentation/manual.php doesn't cover the syntax you are using, MySQL doesn't support your query. In this case, your only options are to implement the syntax yourself or e-mail mysql-licensing@mysql.com and ask for an offer to implement it! If the manual covers the syntax you are using, but you have an older version of MySQL, you should check the MySQL change history to see when the syntax was implemented. In this case, you have the option of upgrading to a newer version of MySQL. See section F MySQL change history.
If you have a problem such that your data appears corrupt or you get errors when you access some particular table, you should first check and then try repairing your tables with myisamchk or CHECK TABLE and REPAIR TABLE. See section 16 Maintaining a MySQL Installation.
If you often get corrupted tables you should try to find out when and why this happens! In this case, the `mysql-data-directory/'hostname'.err' file may contain some information about what happened. See section 23.1 The Error Log. Please include any relevant information from this file in your bug report! Normally mysqld should NEVER crash a table if nothing killed it in the middle of an update! If you can find the cause of mysqld dying, it's much easier for us to provide you with a fix for the problem! See section 21.1 How to Determine What Is Causing Problems.
If possible, download and install the most recent version of MySQL and check whether or not it solves your problem. All versions of MySQL are thoroughly tested and should work without problems! We believe in making everything as backward compatible as possible, and you should be able to switch MySQL versions in minutes! See section 4.3 Which MySQL Version to Use.

If you are a support customer, please cross-post the bug report to mysql-support@mysql.com for higher priority treatment, as well as to the appropriate mailing list to see if someone else has experienced (and perhaps solved) the problem.

For information on reporting bugs in MyODBC, see section 19.4 How to Report Problems with MyODBC.

For solutions to some common problems, see See section 21 Problems and Common Errors.

When answers are sent to you individually and not to the mailing list, it is considered good etiquette to summarize the answers and send the summary to the mailing list so that others may have the benefit of responses you received that helped you solve your problem!

2.4 Guidelines for Answering Question on the Mailing List

If you consider your answer to have broad interest, you may want to post it to the mailing list instead of replying directly to the individual who asked. Try to make your answer general enough that people other than the original poster may benefit from it. When you post to the list, please make sure that your answer is not a duplication of a previous answer.

Try to summarize the essential part of the question in your reply; don't feel obliged to quote the entire original message.

Please don't post mail messages from your browser with HTML mode turned on! Many users don't read mail with a browser!

3 MySQL Licensing and Support

This chapter describes MySQL support and licensing arrangements:

The copyrights under which MySQL is distributed (see section 3.2 Copyrights Used by MySQL)
Sample situations illustrating when a license is required (see section 3.3 Example Licensing Situations)
Support costs (see section 3.4 MySQL Licensing and Support Costs) and support benefits (see section 3.5 Types of Commercial Support)
Commercial licensing costs

3.1 MySQL Licensing Policy

The formal terms of the GPL license can be found at section L GNU General Public License. Basically, our licensing policy and interpretation of the GPL is as follows:

Note that older versions of MySQL are still using a more strict license. See the documentation for that version for more information. If you need a commercial MySQL license, because the GPL license doesn't suit your application, you can buy one at https://order.mysql.com/license.htmy.

For normal internal use, MySQL costs nothing. You do not have to pay us if you do not want to.

A license is required if:

You link a part of the of MySQL that has a GPL Copyright to a program that is not free software (embedded usage of the MySQL server). In this case your application would also become GPL through the clause in the GPL license that acts as a virus. By licensing MySQL from us under a commercial license you will avoid this problem.
You have a commercial application that ONLY works with MySQL and ships the application with the MySQL server. This is because we view this as linking even if it is done over the network.
You have a distribution of MySQL and you don't provide the source code for your copy of the MySQL server, as defined in the GPL license.

A license is NOT required if:

You do not need a license to include the client code in commercial programs. The client part of MySQL licensed with the LGPL GNU Library General Public License. The mysql command-line client includes code from the readline library that is under the GPL.
If your use of MySQL does not require a license, but you like MySQL and want to encourage further development, you are certainly welcome to purchase a license or MySQL support anyway.
If you use MySQL in a commercial context such that you profit by its use, we ask that you further the development of MySQL by purchasing some level of support. We feel that if MySQL helps your business, it is reasonable to ask that you help MySQL. (Otherwise, if you ask us support questions, you are not only using for free something into which we've put a lot a work, you're asking us to provide free support, too.)

For circumstances under which a MySQL license is required, you need a license per machine that runs the mysqld server. However, a multiple-CPU machine counts as a single machine, and there is no restriction on the number of MySQL servers that run on one machine, or on the number of clients concurrently connected to a server running on that machine!

If you have any questions as to whether or not a license is required for your particular use of MySQL, please read this again and then contact us. See section 3.4.2 Contact Information.

If you require a MySQL license, the easiest way to pay for it is to use the license form on MySQL's secure server at https://order.mysql.com/license.htmy. Other forms of payment are discussed in section 3.4.1 Payment information.

3.2 Copyrights Used by MySQL

There are several different copyrights on the MySQL distribution:

The MySQL-specific source needed to build the mysqlclient library is licensed under the LGPL and programs in the `client' directory is GPL. Each file has a header that shows which copyright is used for that file.
The client library and the (GNU getopt) library are covered by the ``GNU LIBRARY GENERAL PUBLIC LICENSE.'' See section M GNU Library General Public License.
Some parts of the source (the regexp library) are covered by a Berkeley-style copyright.
All the source in the server and the (GNU readline) library is covered by the ``GNU GENERAL PUBLIC LICENSE.'' See section L GNU General Public License. This is also available as the file `COPYING' in the distributions.

One goal is that the SQL client library should be free enough that it is possible to add MySQL support into commercial products without a license. For this reason, we chose the LGPL license for the client code.

This means that you can use MySQL for free with any program that uses any of the free software licenses. MySQL is also free for any end user for his own or company usage.

However, if you use MySQL for something important to you, you may want to help secure its development by purchasing licenses or a support contract. See section 3.5 Types of Commercial Support.

3.2.1 Copyright Changes

Version 3.22 of MySQL is still using a more strict license. See the documentation for that version for more information.

3.3 Example Licensing Situations

This section describes some situations illustrating whether or not you must license the MySQL server. Generally these examples involve providing MySQL as an integral part of a product.

Note that a single MySQL license covers any number of CPUs and mysqld servers on a machine! There is no artificial limit on the number of clients that connect to the server in any way.

3.3.1 Selling Products that use MySQL

To determine whether or not you need a MySQL license when selling your application, you should ask whether the proper functioning of your application is dependent on the use of MySQL and whether you include the MySQL server with your product. There are several cases to consider:

Does your application require MySQL to function properly?
If your product requires MySQL, you need a license for any machine that runs the mysqld server. For example, if you've designed your application around MySQL, then you've really made a commercial product that requires the engine, so you need a license.
If your application does not require MySQL, you do not need to obtain a license. For example, if using MySQL just adds some new optional features to your product (such as adding logging to a database if MySQL is used rather than logging to a text file), it should fall within normal use, and a license would not be required.
In other words, you need a license if you sell a product designed specifically for use with MySQL or that requires the MySQL server to function at all. This is true whether or not you provide MySQL for your client as part of your product distribution.
It also depends on what you're doing for the client. Do you plan to provide your client with detailed instructions on installing MySQL with your software? Then your product may be contingent on the use of MySQL; if so, you need to buy a license. If you are simply tying into a database that you expect already to have been installed by the time your software is purchased, then you probably don't need a license.

3.3.2 ISP MySQL Services

Internet Service Providers (ISPs) often host MySQL servers for their customers. With the GPL license this does not require a license.

On the other hand, we do encourage people to use ISPs that have MySQL support, as this will give them the confidence that if they have some problem with their MySQL installation, their ISP will be able to solve the problem for them (in some cases with the help from the MySQL development team).

All ISPs that want to keep themselves up-to-date should subscribe to our announce mailing list so that they can be aware of fatal issues that may be relevant for their MySQL installations.

Note that if the ISP doesn't have a license for MySQL, it should give its customers at least read access to the source of the MySQL installation so that its customer can verify that it is patched correctly.

3.3.3 Running a Web Server Using MySQL

If you use MySQL in conjunction with a Web server on Unix, you don't have to pay for a license.

This is true even if you run a commercial Web server that uses MySQL, because you are not selling an embedded MySQL version yourself. However, in this case we would like you to purchase MySQL support, because MySQL is helping your enterprise.

3.4 MySQL Licensing and Support Costs

Our current license prices are shown below. These prices are now under review because of the change to a GPL copyright. New prices and terms will be posted on the MySQL web site at http://www.mysql.com/ as soon as they are ready.

All prices are in US Dollars. If you pay by credit card, the currency is EURO (European Union Euro) so the prices will differ slightly.

Number of licenses	Per copy	Total
1	200 EURO	200 EURO
10 pack	150 EURO	1500 EURO
50 pack	120 EURO	6000 EURO

For high volume (OEM) purchases, the following prices apply:

Number of licenses	Per copy	Minimum	Minimum payment
100-999	40 EURO	100	4000 EURO
1000-2499	25 EURO	200	5000 EURO
2500-4999	20 EURO	400	8000 EURO

For OEM purchases, you must act as the middle-man for eventual problems or extension requests from your users. We also require that OEM customers have at least an extended e-mail support contract. Note that OEM licenses only apply for products where the user doesn't have direct access to the MySQL server (embedded system). In other words, the MySQL server should only be used with the application that was supplied you.

If you have a low-margin, high-volume product, you can always talk to us about other terms (for example, a percent of the sale price). If you do, please be informative about your product, pricing, market, and any other information that may be relevant.

A full-price license is not a support agreement and includes very minimal support. This means that we try to answer any relevant questions. If the answer is in the documentation, we will direct you to the appropriate section. If you have not purchased a license or support, we probably will not answer at all.

If you discover what we consider a real bug, we are likely to fix it in any case. But if you pay for support we will notify you about the fix status instead of just fixing it in a later release.

More comprehensive support is sold separately. Descriptions of what each level of support includes are given in section 3.5 Types of Commercial Support. Costs for the various types of commercial support are shown below. Support level prices are in EURO (European Union Euro). One EURO is about 1.06 USD.

Type of support	Cost per year
Basic e-mail support. See section 3.5.1 Basic E-mail Support.	EURO 200
Extended e-mail support See section 3.5.2 Extended E-mail Support.	EURO 1000
Login support See section 3.5.3 Login Support.	EURO 2000
Extended login support See section 3.5.4 Extended Login Support.	EURO 5000
Telephone support See section 3.5.5 Telephone Support.	EURO 12000

You may upgrade from any lower level of support to a higher level of support for the difference in price between the two support levels.

We do also provide telephone support (mostly emergency support but also 24/7 support). This support option doesn't however have a fixed price but is negotiated for case to case. If you are interested in this option you can email sales@mysql.com and tell us about your needs.

Note that as our sales staff is very busy, it may take some time until your request is handled. Our support staff does however always answer promptly to support questions!

3.4.1 Payment information

Currently we can take SWIFT payments, checks, or credit cards.

Payment should be made to:

Postgirot Bank AB
105 06 STOCKHOLM, SWEDEN

MySQL AB
BOX 6434
11382 STOCKHOLM, SWEDEN

SWIFT address: PGSI SESS
Account number: 96 77 06 - 3

Specify: license and/or support and your name and e-mail address.

In Europe and Japan you can use EuroGiro (that should be less expensive) to the same account.

If you want to pay by check, make it payable to ``MySQL Finland AB'' and mail it to the address below:

MySQL AB
BOX 6434, Torsgatan 21
11382 STOCKHOLM, SWEDEN

If you want to pay by credit card over the Internet, you can use MySQL AB's secure license form.

You can also print a copy of the license form, fill it in, and send it by fax to:

+46-8-729 69 05

If you want us to bill you, you can use the license form and write ``bill us'' in the comment field. You can also mail a message to sales@mysql.com (not mysql@lists.mysql.com!) with your company information and ask us to bill you.

3.4.2 Contact Information

For commercial licensing, please contact the MySQL licensing team. The much preferred method is by e-mail to licensing@mysql.com. Fax is also possible but handling of these may take much longer (Fax +46-8-729 69 05).

If you represent a business that is interested in partnering with MySQL, please send e-mail to partner@mysql.com.

For timely, precise answers to technical questions about MySQL you should order one of our support contracts. MySQL support is provided by the MySQL developers so the standard is extremely high.

If you are interested in placing a banner advertisement on our Web site, please send e-mail to advertising@mysql.com.

If you are interested in any of the jobs listed in our jobs section, please send e-mail to jobs@mysql.com.

For general discussion amongst our many users, please direct your attention to the appropriate mailing list.

For general information inquires, please send e-mail to info@mysql.com.

For questions or comments about the workings or content of the Web site, please send e-mail to webmaster@mysql.com.

3.5 Types of Commercial Support

The following is true of all support options:

The support is per year.
We will fix, or provide a reasonable workaround for any repeatable bug.
We will give a reasonable effort to find and fix any other MySQL related bug.
The higher level of support contract the more effort we will put into finding a solution to your problems.
The following is true for all support contracts except Basic email support: For non-bug related things, like helping you optimize your queries or your system, extending MySQL with new functionality, etc., we charge 200 EURO/hour, which is deducted from your support contract. In other words, if you have login support (2000 EURO), you can expect us to work up to 10 hours to help you with things like this.

3.5.1 Basic E-mail Support

Basic e-mail support is a very inexpensive support option and should be thought of more as a way to support our development of MySQL than as a real support option. We at MySQL do give a lot of free support in all the different MySQL lists, and the money we get from basic e-mail support is largely used to make this possible.

At this support level, the MySQL mailing lists are the preferred means of communication. Questions normally should be mailed to the primary mailing list (mysql@lists.mysql.com) or one of the other regular lists (for example, win32@lists.mysql.com for Windows-related MySQL questions), as someone else already may have experienced and solved the problem you have. See section 2.2 Asking Questions or Reporting Bugs.

However, by purchasing basic e-mail support, you also have access to the support address mysql-support@mysql.com, which is not available as part of the minimal support that you get by purchasing a MySQL license. This means that for especially critical questions, you can cross-post your message to mysql-support@mysql.com. (If the message contains sensitive data, you should post only to mysql-support@mysql.com.)

REMEMBER! to ALWAYS include your registration number and expiration date when you send a message to mysql-support@mysql.com.

Note that if you have encountered a critical, repeatable bug, and follow the rules outlined in the manual section of how to report bugs and send it to bugs@lists.mysql.com, we promise to try to fix this as soon as possible, regardless of your support level! See section 2.3 How to Report Bugs or Problems.

Basic e-mail support includes the following types of service:

If your question is already answered in the manual, we will inform you of the correct section in which you can find the answer. If the answer is not in the manual, we will point you in the right direction to solve your problem.
We guarantee a timely answer for your e-mail messages. We can't guarantee that we can solve any problem, but at least you will receive an answer if we can contact you by e-mail.
We will help with unexpected problems when you install MySQL from a binary distribution on supported platforms. This level of support does not cover installing MySQL from a source distribution. Supported platforms are those for which MySQL is known to work. See section 4.2 Operating Systems Supported by MySQL.
We will help you with bugs and missing features. Any bugs that are found are fixed for the next MySQL release. If the bug is critical for you, we will mail you a patch for it as soon the bug is fixed. Critical bugs always have the highest priority for us, and we ensure that they are fixed as soon as possible.
Your suggestions for the further development of MySQL will be taken into consideration. By taking email support you have already helped the further development of MySQL. If you want to have more input, upgrade to a higher level of support.
If you want us to help optimize your system, you must upgrade to a higher level of support.

3.5.2 Extended E-mail Support

Extended e-mail support includes everything in basic e-mail support with these additions:

Your e-mail will be dealt with before mail from basic e-mail support users and non-registered users.
Your suggestions for the further development of MySQL will receive strong consideration. Simple extensions that suit the basic goals of MySQL are implemented in a matter of days. By taking extended e-mail support you have already helped the further development of MySQL.
Typical situations that are covered by extended e-mail support are:
- We will answer and (within reason) solve questions that relate to possible bugs in MySQL. As soon as the bug is found and corrected, we will mail a patch for it.
- We will help with unexpected problems when you install MySQL from a source or binary distribution on supported platforms.
- We will answer questions about missing features and offer hints how to work around them.
- We will provide hints on optimizing mysqld for your situation.
You are allowed to influence the priority of items on the MySQL TODO List. See section H MySQL and the future (The TODO). This will ensure that the features you really need will be implemented sooner than they might be otherwise.

3.5.3 Login Support

Your e-mail will be dealt with even before e-mail from extended e-mail support users.
Your suggestions for the further development of MySQL will be taken into very high consideration. Realistic extensions that can be implemented in a couple of hours and that suit the basic goals of MySQL will be implemented as soon as possible.
If you have a very specific problem, we can try to log in on your system to solve the problem ``in place.''
Like any database vendor, we can't guarantee that we can rescue any data from crashed tables, but if the worst happens, we will help you rescue as much as possible. MySQL has proven itself very reliable, but anything is possible due to circumstances beyond our control (for example, if your system crashes or someone kills the server by executing a kill -9 command).
We will provide hints on optimizing your system and your queries.
You are allowed to call a MySQL developer (in moderation) and discuss your MySQL-related problems. This option is however only to be used as a last result during an emergency after we have failed to grasp the total problem with email. To make efficient use of our time we need to first get all facts about the problem, before talking on phone, to be able to work as efficiently as possible on solving the problem.

3.5.4 Extended Login Support

Extended login support includes everything in login support with these additions:

Your e-mail has the highest possible priority.
We will actively examine your system and help you optimize it and your queries. We may also optimize and/or extend MySQL to better suit your needs.
You may also request special extensions just for you. For example:
```
mysql> select MY_FUNC(col1,col2) from table;
```
We will provide a binary distribution of all important MySQL releases for your system, as long as we can get an account on a similar system. In the worst case, we may require access to your system to be able to create a binary distribution.
If you can provide accommodations and pay for traveler fares, you can even get a MySQL developer to visit you and offer you help with your troubles. Extended login support entitles you to one personal encounter per year, but we are always very flexible towards our customers! If the visit takes 16 hours or more, the first 8 hours is without charge. For the hours above 8 hours, you will be charged with a rate that is at least 20 % less than our standard rates.

3.5.5 Telephone Support

Telephone support includes everything in extended login support with these additions:

We will provide you with a dynamic web page showing the current list of MySQL developers that you can phone when you have a critical problem.
For non critical problem, you can request a MySQL developer to phone back within 48 hours to discuss MySQL related issues.

3.5.6 Support for other table handlers

To get support for BDB tables, InnoDB tables or GEMINI tables you have to pay an additional 30% on the standard support price for each of the table handlers you would like to have support for.

We at MySQL AB will help you create a proper bug report for the table handler and submit it to the developers for the specific table handler. We will also do our best to ensure that you will get a timely answer or solution from the developers of the table handler.

Even if we are quite confident that we can solve most problems within a timely manner, we can't guarantee a quick solution for any problems you can get with the different table handlers. We will however do our best to help you get the problem solved.

4 Installing MySQL

This chapter describes how to obtain and install MySQL:

For a list of sites from which you can obtain MySQL, see section 4.1 How to Get MySQL.
To see which platforms are supported, see section 4.2 Operating Systems Supported by MySQL. Please note that not all supported system are equally good for running MySQL on them. On some it is much more robust and efficient than others - see section 4.2 Operating Systems Supported by MySQL for details.
Several versions of MySQL are available in both binary and source distributions. We also provide public access to our current source tree for those who want to see our most recent developments and help us test new code. To determine which version and type of distribution you should use, see section 4.3 Which MySQL Version to Use. When in doubt, use the binary distribution.
Installation instructions for binary and source distributions are described in section 4.6 Installing a MySQL Binary Distribution and section 4.7 Installing a MySQL Source Distribution. Each set of instructions includes a section on system-specific problems you may run into.
For post-installation procedures, see section 4.16 Post-installation Setup and Testing. These procedures apply whether you install MySQL using a binary or source distribution.

4.1 How to Get MySQL

Check the MySQL home page for information about the current version and for downloading instructions.

Our main download mirror is located at:

http://download.sourceforge.net/mirrors/mysql/

If you are interested in becoming a MySQL mirror site, you may anonymously rsync with: rsync://download.sourceforge.net/mysql/. Please send e-mail to webmaster@mysql.com notifying us of your mirror to be added to the list below.

If you have problems downloading from our main site, try using one of the mirrors listed below.

Please report bad or out-of-date mirrors to webmaster@mysql.com.

Europe:

Austria [Univ. of Technology/Vienna] WWW FTP
Bulgaria [online.bg/Sofia] WWW FTP
Czech Republic [Masaryk University in Brno] WWW FTP
Czech Republic [www.sopik.cz] WWW
Czech Republic [www.gin.cz] WWW FTP
Denmark [Borsen] WWW
Denmark [SunSITE] WWW FTP
Estonia [OKinteractive] WWW
France [mtesa.net] WWW
Finland [tonnikala.net] WWW
Germany [Kernelnotes.de, Bonn] WWW FTP
Germany [Wolfenbuettel] WWW FTP
Greece [NTUA, Athens] WWW FTP
Hungary [Xenia] WWW FTP
Iceland [GM] WWW FTP
Italy [feelinglinux.com] WWW
Italy [Teta Srl] WWW
Italy [tzone.it] WWW
Ireland [Esat Net] WWW FTP
Netherlands [Silverpoint] WWW
Netherlands [Widexs BV] WWW FTP
Netherlands [ProServe] WWW
Poland [Sunsite] WWW FTP
Poland [ncservice.com/Gdansk] WWW
Portugal [Netc] WWW FTP
Romania [roedu.net/Bucharest] FTP
Russia [DirectNet] WWW FTP
Russia [Scientific Center/Chernogolovka] FTP
Switzerland [Sunsite] WWW FTP
UK [Omnipotent/UK] WWW FTP
UK [PLiG/UK] WWW FTP
UK [Telekon Internet/UK] FTP
Ukraine [PACO] WWW FTP
Ukraine [ISP Alkar Teleport/Dnepropetrovsk] WWW

North America:

Canada [Tryc] WWW
USA [Hurricane Electric/San Jose] WWW
USA [ValueClick, Los Angeles CA] WWW FTP
USA [Wisconsin University/Wisconsin] WWW FTP
USA [LinuxWired/Scottsdale, AZ] WWW FTP
USA [Venoma.Org/Valdosta, GA] WWW
USA [adgrafix.com/Boston, MA] WWW

South America:

Argentina [bannerlandia.com] WWW FTP
Chile [Vision] WWW
Chile [PSINet] WWW FTP
Chile [Tecnoera] WWW

Asia:

China [Freecode] WWW
China [linuxforum.net] WWW
China [ISL/Hong Kong] WWW
China [xcyber.org/Hong Kong] WWW
South Korea [Webiiz] WWW
South Korea [PanworldNet] WWW
Japan [Soft Agency] WWW
Japan [u-aizu.ac.jp/Aizu] FTP
Singapore [HJC] WWW FTP
Taiwan [TTN] WWW
Taiwan [nctu.edu/HsinChu] WWW

Australia:

Australia [AARNet/Queensland] WWW FTP

Africa:

South-Africa [Mweb] WWW
South Africa [The Internet Solution/Johannesburg] FTP

4.2 Operating Systems Supported by MySQL

We use GNU Autoconf, so it is possible to port MySQL to all modern systems with working Posix threads and a C++ compiler. (To compile only the client code, a C++ compiler is required but not threads.) We use and develop the software ourselves primarily on Sun Solaris (Versions 2.5 - 2.7) and SuSE Linux Version 7.x.

Note that for many operating systems, the native thread support works only in the latest versions. MySQL has been reported to compile sucessfully on the following operating system/thread package combinations:

AIX 4.x with native threads. See section 4.12.15 IBM-AIX notes.
BSDI 2.x with the included MIT-pthreads package. See section 4.12.12 BSD/OS Notes.
BSDI 3.0, 3.1 and 4.x with native threads. See section 4.12.12 BSD/OS Notes.
DEC Unix 4.x with native threads. See section 4.12.6 Alpha-DEC-UNIX Notes (Tru64).
FreeBSD 2.x with the included MIT-pthreads package. See section 4.12.9 FreeBSD Notes.
FreeBSD 3.x and 4.x with native threads. See section 4.12.9 FreeBSD Notes.
HP-UX 10.20 with the included MIT-pthreads package. See section 4.12.16 HP-UX Version 10.20 Notes.
HP-UX 11.x with the native threads. See section 4.12.17 HP-UX Version 11.x Notes.
Linux 2.0+ with LinuxThreads 0.7.1+ or glibc 2.0.7+. See section 4.12.5 Linux Notes (All Linux Versions).
Mac OS X Server. See section 4.12.18 Mac OS X Notes.
NetBSD 1.3/1.4 Intel and NetBSD 1.3 Alpha (Requires GNU make). See section 4.12.10 NetBSD notes.
OpenBSD > 2.5 with native therads. OpenBSD < 2.5 with the included MIT-pthreads package. See section 4.12.11 OpenBSD Notes.
OS/2 Warp 3, FixPack 29 and OS/2 Warp 4, FixPack 4. See section 4.14 OS/2 Notes.
SGI Irix 6.x with native threads. See section 4.12.8 SGI-Irix Notes.
Solaris 2.5 and above with native threads on SPARC and x86. See section 4.12.1 Solaris Notes.
SunOS 4.x with the included MIT-pthreads package. See section 4.12.1 Solaris Notes.
SCO OpenServer with a recent port of the FSU Pthreads package. See section 4.12.13 SCO Notes.
SCO UnixWare 7.0.1. See section 4.12.14 SCO Unixware Version 7.0 Notes.
Tru64 Unix
Win95, Win98, NT, and Win2000. See section 4.13 Windows Notes.

Note that not all platforms are suited equally well for running MySQL. How well a certain platform is suited for a high-load mission critical MySQL server is determined by the following factors:

General stability of the thread library. A platform may have excellent reputation otherwise, but if the thread library is unstable in the code that is called by MySQL, even if everything else is perfect, MySQL will be only as stable as the thread library.
The ability of the kernel and/or thread library to take advantage of SMP on multi-processor systems. In other words, when a process creates a thread, it should be possible for that thread to run on a different CPU than the original process.
The ability of the kernel and/or the thread library to run many threads which acquire/release a mutex over a short critical region frequently without excessive context switches. In other words, if the implementation of pthread_mutex_lock() is too anxious to yield CPU, this will hurt MySQL tremendously. If this issue is not taken care of, adding extra CPUs will actually make MySQL slower.
General file system stability/performance.
Ability of the file system to deal with large files at all and deal with them efficiently, if your tables are big.
Our level of expertise here at MySQL AB with the platform. If we know a platform well, we introduce platform-specific optimizations/fixes enabled at compile time. We can also provide advice on configuring your system optimally for MySQL.
The amount of testing of similar configurations we have done internally.
The number of users that have successfully run MySQL on that platform in similar configurations. If this number is high, the chances of hitting some platform-specific surprise are much smaller.

Based on the above criterea, the best platforms for running MySQL at this point are x86 with SuSE Linux 7.1, 2.4 kernel and ReiserFS (or any similar Linux distribution) and Sparc with Solaris 2.7 or 2.8. FreeBSD comes third, but we really hope it will join the top club once the thread library is improved. We also hope that at some point we will be able to include all other platforms on which MySQL compiles, runs ok, but not quite with the same level of stability and performance, into the top category. This will require some effort on our part in cooperation with the developers of the OS/library components MySQL depends upon. If you are interested in making one of those components better, are in a position to influence their development, and need more detailed instructions on what MySQL needs to run better, send an e-mail to internals@lists.mysql.com.

Please note that the comparison above is not to say that one OS is better or worse than the other in general. We are talking about choosing a particular OS for a dedicated purpose - running MySQL, and compare platforms in that regard only. With this in mind, the result of this comparison would be different if we included more issues into it. And in some cases, the reason one OS is better than the other could simply be that we have put forth more effort into testing on and optimizing for that particular platform. We are just stating our observations to help you make a decision on which platform to use MySQL on in your setup.

4.3 Which MySQL Version to Use

The first decision to make is whether you want to use the latest development release or the last stable release:

Normally, if you are beginning to use MySQL for the first time or trying to port it to some system for which there is no binary distribution, we recommend going with the stable release (currently Version 3.23.37. Note that all MySQL releases are checked with the MySQL benchmarks and an extensive test suite before each release.
Otherwise, if you are running an old system and want to upgrade, but don't want to take chances with a non-seamless upgrade, you should upgrade to the latest in the same branch you are using (where only the last version number is newer than yours). We have tried to fix only fatal bugs and make small, relatively safe changes to that version.

The second decision to make is whether you want to use a source distribution or a binary distribution. In most cases you should probably use a binary distribution, if there exist one for your platform, as this is generally, it will be easier to install than a source distribution.

In the following cases you will probably be better off with a source installation:

If you want to install MySQL at some explicit location. (The standard binary distributions are 'ready to run' at any place, but you may want to get even more flexibility).
To be able to satisfy different user requirements, we are providing two different binary versions; One compiled with the non-transactional table handlers, (a small, fast binary), and one configurated with the most important extended options like transaction safe tables. Both versions are compiled from the same source distribution. All native MySQL clients can connect to both MySQL versions. The extended MySQL binary distribution is marked with the -max suffix and is configured with the same options as mysqld-max. See section 15.2 mysqld-max, An extended mysqld server. If you are want to use the MySQL-Max RPM, you must first install the standard MySQL RPM.
If you want to configure mysqld with some extra feature that is NOT in the standard binary distributions. Here is a list of the most common extra options that you may want to use:
- --with-berkeley-db
- --with-innodb
- --with-raid
- --with-libwrap
- --with-named-z-lib (This is done for some of the binaries)
- --with-debug[=full]
The default binary distribution is normally compiled with support for all characters sets and should work on a variety of processors from the same processor family. If you want a faster MySQL server you may want to recompile it with support for only the character sets you need, use a better compiler (like pgcc) or use compiler options that are better optimized for your processor.
If you have found a bug and reported it to the MySQL development team you will probably receive a patch that you need to apply to the source distribution to get the bug fixed.
If you want to read (and/or modify) the C and C++ code that makes up MySQL, you should get a source distribution. The source code is always the ultimate manual. Source distributions also contain more tests and examples than binary distributions.

The MySQL naming scheme uses release numbers that consist of three numbers and a suffix. For example, a release name like mysql-3.21.17-beta is interpreted like this:

The first number (3) describes the file format. All Version 3 releases have the same file format.
The second number (21) is the release level. Normally there are two to choose from. One is the release/stable branch (currently 23) and the other is the development branch (currently 4.0). Normally both are stable, but the development version may have quirks, missing documentation on new features, or may fail to compile on some systems.
The third number (17) is the version number within the release level. This is incremented for each new distribution. Usually you want the latest version for the release level you have choosen.
The suffix (beta) indicates the stability level of the release. The possible suffixes are:
- alpha indicates that the release contains some large section of new code that hasn't been 100% tested. Known bugs (usually there are none) should be documented in the News section. See section F MySQL change history. There are also new commands and extensions in most alpha releases. Active development that may involve major code changes can occur on an alpha release, but everything will be tested before doing a release. There should be no known bugs in any MySQL release.
- beta means that all new code has been tested. No major new features that could cause corruption on old code are added. There should be no known bugs. A version changes from alpha to beta when there haven't been any reported fatal bugs within an alpha version for at least a month and we don't plan to add any features that could make any old command more unreliable.
- gamma is a beta that has been around a while and seems to work fine. Only minor fixes are added. This is what many other companies call a release.
- If there is no suffix, it means that the version has been run for a while at many different sites with no reports of bugs other than platform-specific bugs. Only critical bug fixes are applied to the release. This is what we call a stable release.

All versions of MySQL are run through our standard tests and benchmarks to ensure that they are relatively safe to use. Because the standard tests are extended over time to check for all previously found bugs, the test suite keeps getting better.

Note that all releases have been tested at least with:

An internal test suite: This is part of a production system for a customer. It has many tables with hundreds of megabytes of data.
The MySQL benchmark suite: This runs a range of common queries. It is also a test to see whether the latest batch of optimizations actually made the code faster. See section 13.7 Using Your Own Benchmarks.
The crash-me test: This tries to determine what features the database supports and what its capabilities and limitations are. See section 13.7 Using Your Own Benchmarks.

Another test is that we use the newest MySQL version in our internal production environment, on at least one machine. We have more than 100 gigabytes of data to work with.

4.4 How and When Updates Are Released

MySQL is evolving quite rapidly here at MySQL AB and we want to share this with other MySQL users. We try to make a release when we have very useful features that others seem to have a need for.

We also try to help out users who request features that are easy to implement. We take note of what our licensed users want to have, and we especially take note of what our extended e-mail supported customers want and try to help them out.

No one has to download a new release. The News section will tell you if the new release has something you really want. See section F MySQL change history.

We use the following policy when updating MySQL:

For each minor update, the last number in the version string is incremented. When there are major new features or minor incompatibilities with previous versions, the second number in the version string is incremented. When the file format changes, the first number is increased.
Stable tested releases are meant to appear about 1-2 times a year, but if small bugs are found, a release with only bug fixes will be released.
Working releases are meant to appear about every 1-8 weeks.
Binary distributions for some platforms will be made by us for major releases. Other people may make binary distributions for other systems but probably less frequently.
We usually make patches available as soon as we have located and fixed small bugs.
For non-critical but annoying bugs, we will make patches available if they are sent to us. Otherwise we will combine many of them into a larger patch.
If there is, by any chance, a fatal bug in a release we will make a new release as soon as possible. We would like other companies to do this, too.

The current stable release is Version 3.23; We have already moved active development to Version 4.0. Bugs will still be fixed in the stable version. We don't believe in a complete freeze, as this also leaves out bug fixes and things that ``must be done.'' ``Somewhat frozen'' means that we may add small things that ``almost surely will not affect anything that's already working.''

4.5 Installation Layouts

This section describes the default layout of the directories created by installing binary and source distributions.

A binary distribution is installed by unpacking it at the installation location you choose (typically `/usr/local/mysql') and creates the following directories in that location:

Directory	Contents of directory
`bin'	Client programs and the `mysqld` server
`data'	Log files, databases
`include'	Include (header) files
`lib'	Libraries
`scripts'	`mysql_install_db`
`share/mysql'	Error message files
`sql-bench'	Benchmarks

A source distribution is installed after you configure and compile it. By default, the installation step installs files under `/usr/local', in the following subdirectories:

Directory	Contents of directory
`bin'	Client programs and scripts
`include/mysql'	Include (header) files
`info'	Documentation in Info format
`lib/mysql'	Libraries
`libexec'	The `mysqld` server
`share/mysql'	Error message files
`sql-bench'	Benchmarks and `crash-me` test
`var'	Databases and log files

Within an installation directory, the layout of a source installation differs from that of a binary installation in the following ways:

The mysqld server is installed in the `libexec' directory rather than in the `bin' directory.
The data directory is `var' rather than `data'.
mysql_install_db is installed in the `/usr/local/bin' directory rather than in `/usr/local/mysql/scripts'.
The header file and library directories are `include/mysql' and `lib/mysql' rather than `include' and `lib'.

You can create your own binary installation from a compiled source distribution by executing the script `scripts/make_binary_distribution'.

4.6 Installing a MySQL Binary Distribution

You need the following tools to install a MySQL binary distribution:

GNU gunzip to uncompress the distribution.
A reasonable tar to unpack the distribution. GNU tar is known to work. Sun tar is known to have problems.

An alternative installation method under Linux is to use RPM (RedHat Package Manager) distributions. See section 4.6.1 Linux RPM Notes.

If you run into problems, PLEASE ALWAYS USE mysqlbug when posting questions to mysql@lists.mysql.com. Even if the problem isn't a bug, mysqlbug gathers system information that will help others solve your problem. By not using mysqlbug, you lessen the likelihood of getting a solution to your problem! You will find mysqlbug in the `bin' directory after you unpack the distribution. See section 2.3 How to Report Bugs or Problems.

The basic commands you must execute to install and use a MySQL binary distribution are:

shell> groupadd mysql
shell> useradd -g mysql mysql
shell> cd /usr/local
shell> gunzip < /path/to/mysql-VERSION-OS.tar.gz | tar xvf -
shell> ln -s mysql-VERSION-OS mysql
shell> cd mysql
shell> scripts/mysql_install_db
shell> chown -R root  /usr/local/mysql
shell> chown -R mysql /usr/local/mysql/data
shell> chgrp -R mysql /usr/local/mysql
shell> chown -R root /usr/local/mysql/bin/
shell> bin/safe_mysqld --user=mysql &

You can add new users using the bin/mysql_setpermission script if you install the DBI and Msql-Mysql-modules Perl modules.

A more detailed description follows.

To install a binary distribution, follow the steps below, then proceed to section 4.16 Post-installation Setup and Testing, for post-installation setup and testing:

Pick the directory under which you want to unpack the distribution, and move into it. In the example below, we unpack the distribution under `/usr/local' and create a directory `/usr/local/mysql' into which MySQL is installed. (The following instructions therefore assume you have permission to create files in `/usr/local'. If that directory is protected, you will need to perform the installation as root.)
Obtain a distribution file from one of the sites listed in section 4.1 How to Get MySQL. MySQL binary distributions are provided as compressed tar archives and have names like `mysql-VERSION-OS.tar.gz', where VERSION is a number (for example, 3.21.15), and OS indicates the type of operating system for which the distribution is intended (for example, pc-linux-gnu-i586).
If you see a binary distribution marked with the -max prefix, this means that the binary has support for transaction safe tables and other features. See section 15.2 mysqld-max, An extended mysqld server. Note that all binaries are built from the same MySQL source distribution.
Add a user and group for mysqld to run as:
```
shell> groupadd mysql
shell> useradd -g mysql mysql
```
These commands add the mysql group and the mysql user. The syntax for useradd and groupadd may differ slightly on different Unixes. They may also be called adduser and addgroup. You may wish to call the user and group something else instead of mysql.
Change into the intended installation directory:
```
shell> cd /usr/local
```
Unpack the distribution and create the installation directory:
```
shell> gunzip < /path/to/mysql-VERSION-OS.tar.gz | tar xvf -
shell> ln -s mysql-VERSION-OS mysql
```
The first command creates a directory named `mysql-VERSION-OS'. The second command makes a symbolic link to that directory. This lets you refer more easily to the installation directory as `/usr/local/mysql'.
Change into the installation directory:
```
shell> cd mysql
```
You will find several files and subdirectories in the mysql directory. The most important for installation purposes are the `bin' and `scripts' subdirectories.

`bin'
This directory contains client programs and the server You should add the full pathname of this directory to your PATH environment variable so that your shell finds the MySQL programs properly. See section A Environment Variables.
`scripts'
This directory contains the mysql_install_db script used to initialize the server access permissions.
If you would like to use mysqlaccess and have the MySQL distribution in some non-standard place, you must change the location where mysqlaccess expects to find the mysql client. Edit the `bin/mysqlaccess' script at approximately line 18. Search for a line that looks like this:
```
$MYSQL     = '/usr/local/bin/mysql';    # path to mysql executable
```
Change the path to reflect the location where mysql actually is stored on your system. If you do not do this, you will get a Broken pipe error when you run mysqlaccess.
Create the MySQL grant tables (necessary only if you haven't installed MySQL before):
```
shell> scripts/mysql_install_db
```
Note that MySQL versions older than Version 3.22.10 started the MySQL server when you run mysql_install_db. This is no longer true!
Change ownership of binaries to root and ownership of the data directory to the user that you will run mysqld as:
```
shell> chown -R root  /usr/local/mysql
shell> chown -R mysql /usr/local/mysql/var
shell> chgrp -R mysql /usr/local/mysql
```
The first command changes the owner attribute of the files to the root user, the second one changes the owner attribute of the data directory to the mysql user, and the third one changes the group attribute to the mysql group.
If you want to install support for the Perl DBI/DBD interface, see section 4.11 Perl Installation Comments.
If you would like MySQL to start automatically when you boot your machine, you can copy support-files/mysql.server to the location where your system has its startup files. More information can be found in the support-files/mysql.server script itself and in section 4.16.3 Starting and Stopping MySQL Automatically.

After everything has been unpacked and installed, you should initialize and test your distribution.

You can start the MySQL server with the following command:

shell> bin/safe_mysqld --user=mysql &

See section 15.3 safe_mysqld, the wrapper around mysqld.

See section 4.16 Post-installation Setup and Testing.

4.6.1 Linux RPM Notes

The recommended way to install MySQL on Linux is by using an RPM file. The MySQL RPMs are currently being built on a RedHat Version 6.2 system but should work on other versions of Linux that support rpm and use glibc.

If you have problems with an RPM file, for example, if you receive the error ``Sorry, the host 'xxxx' could not be looked up'', see section 4.6.3.1 Linux Notes for Binary Distributions.

The RPM files you may want to use are:

MySQL-VERSION.i386.rpm The MySQL server. You will need this unless you only want to connect to a MySQL server running on another machine.
MySQL-client-VERSION.i386.rpm The standard MySQL client programs. You probably always want to install this package.
MySQL-bench-VERSION.i386.rpm Tests and benchmarks. Requires Perl and msql-mysql-modules RPMs.
MySQL-devel-VERSION.i386.rpm Libraries and include files needed if you want to compile other MySQL clients, such as the Perl modules.
MySQL-VERSION.src.rpm This contains the source code for all of the above packages. It can also be used to try to build RPMs for other architectures (for example, Alpha or SPARC).

To see all files in an RPM package, run:

shell> rpm -qpl MySQL-VERSION.i386.rpm

To perform a standard minimal installation, run:

shell> rpm -i MySQL-VERSION.i386.rpm MySQL-client-VERSION.i386.rpm

To install just the client package, run:

shell> rpm -i MySQL-client-VERSION.i386.rpm

The RPM places data in `/var/lib/mysql'. The RPM also creates the appropriate entries in `/etc/rc.d/' to start the server automatically at boot time. (This means that if you have performed a previous installation, you may want to make a copy of your previously installed MySQL startup file if you made any changes to it, so you don't lose your changes.)

After installing the RPM file(s), the `mysqld' daemon should be running and you should now be able to start using MySQL. See section 4.16 Post-installation Setup and Testing.

If something goes wrong, you can find more information in the binary installation chapter. See section 4.6 Installing a MySQL Binary Distribution.

4.6.2 Building Client Programs

If you compile MySQL clients that you've written yourself or that you obtain from a third party, they must be linked using the -lmysqlclient -lz option on the link command. You may also need to specify a -L option to tell the linker where to find the library. For example, if the library is installed in `/usr/local/mysql/lib', use -L/usr/local/mysql/lib -lmysqlclient -lz on the link command.

For clients that use MySQL header files, you may need to specify a -I option when you compile them (for example, -I/usr/local/mysql/include), so the compiler can find the header files.

4.6.3 System-specific Issues

The following sections indicate some of the issues that have been observed on particular systems when installing MySQL from a binary distribution.

4.6.3.1 Linux Notes for Binary Distributions

MySQL needs at least Linux Version 2.0.

The binary release is linked with -static, which means you do not normally need to worry about which version of the system libraries you have. You need not install LinuxThreads, either. A program linked with -static is slightly bigger than a dynamically linked program but also slightly faster (3-5%). One problem, however, is that you can't use user-definable functions (UDFs) with a statically linked program. If you are going to write or use UDF functions (this is something only for C or C++ programmers), you must compile MySQL yourself, using dynamic linking.

If you are using a libc-based system (instead of a glibc2 system), you will probably get some problems with hostname resolving and getpwnam() with the binary release. (This is because glibc unfortunately depends on some external libraries to resolve hostnames and getpwent(), even when compiled with -static). In this case you probably get the following error message when you run mysql_install_db:

Sorry, the host 'xxxx' could not be looked up

or the following error when you try to run mysqld with the --user option:

getpwnam: No such file or directory

You can solve this problem in one of the following ways:

Get a MySQL source distribution (an RPM or the tar.gz distribution) and install this instead.
Execute mysql_install_db --force; This will not execute the resolveip test in mysql_install_db. The downside is that you can't use host names in the grant tables; you must use IP numbers instead (except for localhost). If you are using an old MySQL release that doesn't support --force, you have to remove the resolveip test in mysql_install with an editor.
Start mysqld with su instead of using --user.

The Linux-Intel binary and RPM releases of MySQL are configured for the highest possible speed. We are always trying to use the fastest stable compiler available.

MySQL Perl support requires Version Perl 5.004_03 or newer.

On some Linux 2.2 versions, you may get the error Resource temporarily unavailable when you do a lot of new connections to a mysqld server over TCP/IP.

The problem is that Linux has a delay between when you close a TCP/IP socket and until this is actually freed by the system. As there is only room for a finite number of TCP/IP slots, you will get the above error if you try to do too many new TCP/IP connections during a small time, like when you run the MySQL `test-connect' benchmark over TCP/IP.

We have mailed about this problem a couple of times to different Linux mailing lists but have never been able to resolve this properly.

The only known 'fix' to this problem is to use persistent connections in your clients or use sockets, if you are running the database server and clients on the same machine. We hope that the Linux 2.4 kernel will fix this problem in the future.

4.6.3.2 HP-UX Notes for Binary Distributions

Some of the binary distributions of MySQL for HP-UX is distributed as an HP depot file and as a tar file. To use the depot file you must be running at least HP-UX 10.x to have access to HP's software depot tools.

The HP version of MySQL was compiled on an HP 9000/8xx server under HP-UX 10.20, and uses MIT-pthreads. It is known to work well under this configuration. MySQL Version 3.22.26 and newer can also be built with HP's native thread package.

Other configurations that may work:

HP 9000/7xx running HP-UX 10.20+
HP 9000/8xx running HP-UX 10.30

The following configurations almost definitely won't work:

HP 9000/7xx or 8xx running HP-UX 10.x where x < 2
HP 9000/7xx or 8xx running HP-UX 9.x

To install the distribution, use one of the commands below, where /path/to/depot is the full pathname of the depot file:

To install everything, including the server, client and development tools:
```
shell> /usr/sbin/swinstall -s /path/to/depot mysql.full
```

To install only the server:

shell> /usr/sbin/swinstall -s /path/to/depot mysql.server

To install only the client package:

shell> /usr/sbin/swinstall -s /path/to/depot mysql.client

To install only the development tools:

shell> /usr/sbin/swinstall -s /path/to/depot mysql.developer

The depot places binaries and libraries in `/opt/mysql' and data in `/var/opt/mysql'. The depot also creates the appropriate entries in `/etc/init.d' and `/etc/rc2.d' to start the server automatically at boot time. Obviously, this entails being root to install.

To install the HP-UX tar.gz distribution, you must have a copy of GNU tar.

4.7 Installing a MySQL Source Distribution

Before you proceed with the source installation, check first to see if our binary is available for your platform and if it will work for you. We put in a lot of effort into making sure that our binaries are built with the best possible options.

You need the following tools to build and install MySQL from source:

GNU gunzip to uncompress the distribution.
A reasonable tar to unpack the distribution. GNU tar is known to work. Sun tar is known to have problems.
A working ANSI C++ compiler. gcc >= 2.8.1, egcs >= 1.0.2, SGI C++, and SunPro C++ are some of the compilers that are known to work. libg++ is not needed when using gcc. gcc 2.7.x has a bug that makes it impossible to compile some perfectly legal C++ files, such as `sql/sql_base.cc'. If you only have gcc 2.7.x, you must upgrade your gcc to be able to compile MySQL. gcc >= 2.95.2 is recommended when compiling MySQL Version 3.23.x.
A good make program. GNU make is always recommended and is sometimes required. If you have problems, we recommend trying GNU make 3.75 or newer.

If you are using a recent version of gcc, recent enough to understand -fno-exceptions option, it is VERY IMPORTANT that you use it. Otherwise, you may compile a binary that crashes randomly. We also recommend that you use -felide-contructors and -fno-rtti along with -fno-exceptions. When in doubt, do the following:


CFLAGS="-O3" CXX=gcc CXXFLAGS="-O3 -felide-constructors -fno-exceptions -fno-rtti" ./configure --prefix=/usr/local/mysql --enable-assembler --with-mysqld-ldflags=-all-static

On most systems this will give you a fast and stable binary.

If you run into problems, PLEASE ALWAYS USE mysqlbug when posting questions to mysql@lists.mysql.com. Even if the problem isn't a bug, mysqlbug gathers system information that will help others solve your problem. By not using mysqlbug, you lessen the likelihood of getting a solution to your problem! You will find mysqlbug in the `scripts' directory after you unpack the distribution. See section 2.3 How to Report Bugs or Problems.

4.7.1 Quick Installation Overview

The basic commands you must execute to install a MySQL source distribution are:

shell> groupadd mysql
shell> useradd -g mysql mysql
shell> gunzip < mysql-VERSION.tar.gz | tar -xvf -
shell> cd mysql-VERSION
shell> ./configure --prefix=/usr/local/mysql
shell> make
shell> make install
shell> scripts/mysql_install_db
shell> chown -R root  /usr/local/mysql
shell> chown -R mysql /usr/local/mysql/var
shell> chgrp -R mysql /usr/local/mysql
shell> /usr/local/mysql/bin/safe_mysqld --user=mysql &

If you start from a source RPM, then do the following:

shell> rpm --rebuild MySQL-VERSION.src.rpm

This will make a binary RPM that you can install.

You can add new users using the bin/mysql_setpermission script if you install the DBI and Msql-Mysql-modules Perl modules.

A more detailed description follows.

To install a source distribution, follow the steps below, then proceed to section 4.16 Post-installation Setup and Testing, for post-installation initialization and testing:

Pick the directory under which you want to unpack the distribution, and move into it.
Obtain a distribution file from one of the sites listed in section 4.1 How to Get MySQL.
If you are interested in using Berkeley DB tables with MySQL, you will need to obtain a patched version of the Berkeley DB source code. Please read the chapter on Berkeley DB tables before proceeding. See section 8.5 BDB or Berkeley_DB Tables. MySQL source distributions are provided as compressed tar archives and have names like `mysql-VERSION.tar.gz', where VERSION is a number like 3.23.37.
Add a user and group for mysqld to run as:
```
shell> groupadd mysql
shell> useradd -g mysql mysql
```
These commands add the mysql group, and the mysql user. The syntax for useradd and groupadd may differ slightly on different Unixes. They may also be called adduser and addgroup. You may wish to call the user and group something else instead of mysql.
Unpack the distribution into the current directory:
```
shell> gunzip < /path/to/mysql-VERSION.tar.gz | tar xvf -
```
This command creates a directory named `mysql-VERSION'.
Change into the top-level directory of the unpacked distribution:
```
shell> cd mysql-VERSION
```
Note that currently you must configure and build MySQL from this top-level directory. You can not build it in a different directory.
Configure the release and compile everything:
```
shell> ./configure --prefix=/usr/local/mysql
shell> make
```
When you run configure, you might want to specify some options. Run ./configure --help for a list of options. section 4.7.3 Typical configure Options, discusses some of the more useful options. If configure fails, and you are going to send mail to mysql@lists.mysql.com to ask for assistance, please include any lines from `config.log' that you think can help solve the problem. Also include the last couple of lines of output from configure if configure aborts. Post the bug report using the mysqlbug script. See section 2.3 How to Report Bugs or Problems. If the compile fails, see section 4.9 Problems Compiling?, for help with a number of common problems.
Install everything:
```
shell> make install
```
You might need to run this command as root.
Create the MySQL grant tables (necessary only if you haven't installed MySQL before):
```
shell> scripts/mysql_install_db
```
Note that MySQL versions older than Version 3.22.10 started the MySQL server when you run mysql_install_db. This is no longer true!
Change ownership of binaries to root and ownership of the data directory to the user that you will run mysqld as:
```
shell> chown -R root  /usr/local/mysql
shell> chown -R mysql /usr/local/mysql/var
shell> chgrp -R mysql /usr/local/mysql
```
The first command changes the owner attribute of the files to the root user, the second one changes the owner attribute of the data directory to the mysql user, and the third one changes the group attribute to the mysql group.
If you want to install support for the Perl DBI/DBD interface, see section 4.11 Perl Installation Comments.
If you would like MySQL to start automatically when you boot your machine, you can copy support-files/mysql.server to the location where your system has its startup files. More information can be found in the support-files/mysql.server script itself and in section 4.16.3 Starting and Stopping MySQL Automatically.

After everything has been installed, you should initialize and test your distribution:

shell> /usr/local/mysql/bin/safe_mysqld --user=mysql &

If that command fails immediately with mysqld daemon ended then you can find some information in the file `mysql-data-directory/'hostname'.err'. The likely reason is that you already have another mysqld server running. See section 22.3 Running Multiple MySQL Servers on the Same Machine.

See section 4.16 Post-installation Setup and Testing.

4.7.2 Applying Patches

Sometimes patches appear on the mailing list or are placed in the patches area of the MySQL Web site.

To apply a patch from the mailing list, save the message in which the patch appears in a file, change into the top-level directory of your MySQL source tree, and run these commands:

shell> patch -p1 < patch-file-name
shell> rm config.cache
shell> make clean

Patches from the FTP site are distributed as plain text files or as files compressed with gzip. Apply a plain patch as shown above for mailing list patches. To apply a compressed patch, change into the top-level directory of your MySQL source tree and run these commands:

shell> gunzip < patch-file-name.gz | patch -p1
shell> rm config.cache
shell> make clean

After applying a patch, follow the instructions for a normal source install, beginning with the ./configure step. After running the make install step, restart your MySQL server.

You may need to bring down any currently running server before you run make install. (Use mysqladmin shutdown to do this.) Some systems do not allow you to install a new version of a program if it replaces the version that is currently executing.

4.7.3 Typical `configure` Options

The configure script gives you a great deal of control over how you configure your MySQL distribution. Typically you do this using options on the configure command line. You can also affect configure using certain environment variables. See section A Environment Variables. For a list of options supported by configure, run this command:

shell> ./configure --help

Some of the more commonly-used configure options are described below:

To compile just the MySQL client libraries and client programs and not the server, use the --without-server option:
```
shell> ./configure --without-server
```
If you don't have a C++ compiler, mysql will not compile (it is the one client program that requires C++). In this case, you can remove the code in configure that tests for the C++ compiler and then run ./configure with the --without-server option. The compile step will still try to build mysql, but you can ignore any warnings about `mysql.cc'. (If make stops, try make -k to tell it to continue with the rest of the build even if errors occur.)
If you don't want your log files and database directories located under `/usr/local/var', use a configure command, something like one of these:
```
shell> ./configure --prefix=/usr/local/mysql
shell> ./configure --prefix=/usr/local \
           --localstatedir=/usr/local/mysql/data
```
The first command changes the installation prefix so that everything is installed under `/usr/local/mysql' rather than the default of `/usr/local'. The second command preserves the default installation prefix, but overrides the default location for database directories (normally `/usr/local/var') and changes it to /usr/local/mysql/data.
If you are using Unix and you want the MySQL socket located somewhere other than the default location (normally in the directory `/tmp' or `/var/run') use a configure command like this:
```
shell> ./configure --with-unix-socket-path=/usr/local/mysql/tmp/mysql.sock
```
Note that the given file must be an absolute pathname!
If you want to compile statically linked programs (for example, to make a binary distribution, to get more speed, or to work around problems with some RedHat Linux distributions), run configure like this:
```
shell> ./configure --with-client-ldflags=-all-static \
           --with-mysqld-ldflags=-all-static
```

If you are using gcc and don't have libg++ or libstdc++ installed, you can tell configure to use gcc as your C++ compiler:

shell> CC=gcc CXX=gcc ./configure

When you use gcc as your C++ compiler, it will not attempt to link in libg++ or libstdc++. Here is some common environment variables to set depending on the compiler you are using:

gcc 2.7.2.1	CC=gcc CXX=gcc CXXFLAGS="-O3 -felide-constructors"
egcs 1.0.3a	CC=gcc CXX=gcc CXXFLAGS="-O3 -felide-constructors -fno-exceptions -fno-rtti"
gcc 2.95.2	CFLAGS="-O3 -mpentiumpro" CXX=gcc CXXFLAGS="-O3 -mpentiumpro -felide-constructors -fno-exceptions -fno-rtti"
pgcc 2.90.29 or newer	CFLAGS="-O3 -mpentiumpro -mstack-align-double" CXX=gcc CXXFLAGS="-O3 -mpentiumpro -mstack-align-double -felide-constructors -fno-exceptions -fno-rtti"

In most cases you can get a reasonably optimal MySQL binary by using the options from the above and adding the following options to the configure line:

--prefix=/usr/local/mysql --enable-assembler --with-mysqld-ldflags=-all-static

The full configure line would in other words be something like the following for all recent gcc versions:

CFLAGS="-O3 -mpentiumpro" CXX=gcc CXXFLAGS="-O3 -mpentiumpro -felide-constructors -fno-exceptions -fno-rtti" ./configure --prefix=/usr/local/mysql --enable-assembler --with-mysqld-ldflags=-all-static

The binaries we provide on the MySQL Web site at http://www.mysql.com are all compiled with full optimization and should be perfect for most users. See section 4.15 MySQL Binaries. There are some things you can tweak to make an even faster binary, but this is only for advanced users. See section 13.2.1 How Compiling and Linking Affects the Speed of MySQL. If the build fails and produces errors about your compiler or linker not being able to create the shared library `libmysqlclient.so.#' (`#' is a version number), you can work around this problem by giving the --disable-shared option to configure. In this case, configure will not build a shared libmysqlclient.so.# library.

You can configure MySQL not to use DEFAULT column values for non-NULL columns (that is, columns that are not allowed to be NULL). This causes INSERT statements to generate an error unless you explicitly specify values for all columns that require a non-NULL value. To suppress use of default values, run configure like this:
```
shell> CXXFLAGS=-DDONT_USE_DEFAULT_FIELDS ./configure
```
By default, MySQL uses the ISO-8859-1 (Latin1) character set. To change the default set, use the --with-charset option:
```
shell> ./configure --with-charset=CHARSET
```
CHARSET may be one of big5, cp1251, cp1257, czech, danish, dec8, dos, euc_kr, gb2312, gbk, german1, hebrew, hp8, hungarian, koi8_ru, koi8_ukr, latin1, latin2, sjis, swe7, tis620, ujis, usa7, or win1251ukr. See section 10.1.1 The Character Set Used for Data and Sorting. If you want to convert characters between the server and the client, you should take a look at the SET OPTION CHARACTER SET command. See section 7.33 SET Syntax. Warning: If you change character sets after having created any tables, you will have to run myisamchk -r -q on every table. Your indexes may be sorted incorrectly otherwise. (This can happen if you install MySQL, create some tables, then reconfigure MySQL to use a different character set and reinstall it.)
To configure MySQL with debugging code, use the --with-debug option:
```
shell> ./configure --with-debug
```
This causes a safe memory allocator to be included that can find some errors and that provides output about what is happening. See section I.1 Debugging a MySQL server.
If your client programs are using threads, you need to also compile a thread-safe version of the MySQL client library with the --with-thread-safe-client configure options. This will create a libmysqlclient_r library with which you should link your threaded applications. See section 24.1.5 How to Make a Thread-safe Client.
Options that pertain to particular systems can be found in the system-specific sections later in this chapter. See section 4.12 System-specific Issues.

4.8 Installing from development source tree

CAUTION: You should only read this section if you are interested in helping us test our new code. If you just want to get MySQL up and running on your system, you should use either source or binary distribution.

Below are the instructions to obtain our most recent development source tree:

Download BitKeeper from http://www.bitmover.com/cgi-bin/download.cgi. You will need Bitkeeper 2.0 or newer to access our repository.
Follow the instructions to install it.
Once BitKeeper is installed, if you want to clone 3.23 branch, bk clone bk://work.mysql.com:7000 mysql, and bk clone bk://work.mysql.com:7001 mysql-4.0 for 4.0 branch. The initial download may take a while, depending on the speed of your connection.
You will need GNU autoconf, automake, libtool, and m4 to do the next stage. If you get some strange error during the first stage, check that you really have libtool installed!
```
cd mysql
bk -r edit
aclocal; autoheader; autoconf;  automake;
./configure  # Add your favorite options here
make
```
We have a collection of our standard configure scripts in the `BUILD/' subdirectory. If you are lazy, you can use `BUILD/compile-pentium-debug'. It will actually work on a lot of non-x86 machines despite its name.
Once the build is done, make install. Be careful with this on a production machine - this may overwrite your live release binary. We recommend that if you have another installation of MySQL that you ./configure with different values for prefix, tcp-port, and unix-socket-path.
Play hard with your new installation and try to make the new features crash. Start by running make test. See section 26.2 MySQL Test Suite.
If you have gotten to the make stage and it does not compile, please report it to bugs@lists.mysql.com. If you have installed the latest version of the required GNU tools, and they crash trying to process our configuration files, please report it also. However, if you execute aclocal and get command not found, or a similar problem, do not report it, make sure all the needed tools are installed and your PATH variable is set correctly.
After the initial bk clone, do bk pull to get the updates.
You can examine change history of the tree with all the diffs with bk sccstool. If you see some funny diffs or code that you have a question about, do not hesitate and e-mail internals@lists.mysql.com. Also if you think you have a better idea on how to do something, send an email to the same place with a patch. bk diffs will produce a patch for you after you have made changes to the source. If you do not have the time to code your idea, just send a description.
BitKeeper has a nice help utility that you can access via bk helptool.

4.9 Problems Compiling?

All MySQL programs compile cleanly for us with no warnings on Solaris using gcc. On other systems, warnings may occur due to differences in system include files. See section 4.10 MIT-pthreads Notes for warnings that may occur when using MIT-pthreads. For other problems, check the list below.

The solution to many problems involves reconfiguring. If you do need to reconfigure, take note of the following:

If configure is run after it already has been run, it may use information that was gathered during its previous invocation. This information is stored in `config.cache'. When configure starts up, it looks for that file and reads its contents if it exists, on the assumption that the information is still correct. That assumption is invalid when you reconfigure.
Each time you run configure, you must run make again to recompile. However, you may want to remove old object files from previous builds first, because they were compiled using different configuration options.

To prevent old configuration information or object files from being used, run these commands before rerunning configure:

shell> rm config.cache
shell> make clean

Alternatively, you can run make distclean.

The list below describes some of the problems compiling MySQL that have been found to occur most often:

If you get errors when compiling `sql_yacc.cc', such as the ones shown below, you have probably run out of memory or swap space:
```
Internal compiler error: program cc1plus got fatal signal 11
  or
Out of virtual memory
  or
Virtual memory exhausted
```
The problem is that gcc requires huge amounts of memory to compile `sql_yacc.cc' with inline functions. Try running configure with the --with-low-memory option:
```
shell> ./configure --with-low-memory
```
This option causes -fno-inline to be added to the compile line if you are using gcc and -O0 if you are using something else. You should try the --with-low-memory option even if you have so much memory and swap space that you think you can't possibly have run out. This problem has been observed to occur even on systems with generous hardware configurations, and the --with-low-memory option usually fixes it.
By default, configure picks c++ as the compiler name and GNU c++ links with -lg++. If you are using gcc, that behavior can cause problems during configuration such as this:
```
configure: error: installation or configuration problem:
C++ compiler cannot create executables.
```
You might also observe problems during compilation related to g++, libg++, or libstdc++. One cause of these problems is that you may not have g++, or you may have g++ but not libg++, or libstdc++. Take a look at the `config.log' file. It should contain the exact reason why your c++ compiler didn't work! To work around these problems, you can use gcc as your C++ compiler. Try setting the environment variable CXX to "gcc -O3". For example:
```
shell> CXX="gcc -O3" ./configure
```
This works because gcc compiles C++ sources as well as g++ does, but does not link in libg++ or libstdc++ by default. Another way to fix these problems, of course, is to install g++, libg++ and libstdc++.
If your compile fails with errors, such as any of the following, you must upgrade your version of make to GNU make:
```
making all in mit-pthreads
make: Fatal error in reader: Makefile, line 18:
Badly formed macro assignment
  or
make: file `Makefile' line 18: Must be a separator (:
  or
pthread.h: No such file or directory
```
Solaris and FreeBSD are known to have troublesome make programs. GNU make Version 3.75 is known to work.
If you want to define flags to be used by your C or C++ compilers, do so by adding the flags to the CFLAGS and CXXFLAGS environment variables. You can also specify the compiler names this way using CC and CXX. For example:
```
shell> CC=gcc
shell> CFLAGS=-O3
shell> CXX=gcc
shell> CXXFLAGS=-O3
shell> export CC CFLAGS CXX CXXFLAGS
```
See section 4.15 MySQL Binaries, for a list of flag definitions that have been found to be useful on various systems.
If you get an error message like this, you need to upgrade your gcc compiler:
```
client/libmysql.c:273: parse error before `__attribute__'
```
gcc 2.8.1 is known to work, but we recommend using gcc 2.95.2 or egcs 1.0.3a instead.
If you get errors such as those shown below when compiling mysqld, configure didn't correctly detect the type of the last argument to accept(), getsockname(), or getpeername():
```
cxx: Error: mysqld.cc, line 645: In this statement, the referenced
     type of the pointer value "&length" is "unsigned long", which
     is not compatible with "int".
new_sock = accept(sock, (struct sockaddr *)&cAddr, &length);
```
To fix this, edit the `config.h' file (which is generated by configure). Look for these lines:
```
/* Define as the base type of the last arg to accept */
#define SOCKET_SIZE_TYPE XXX
```
Change XXX to size_t or int, depending on your operating system. (Note that you will have to do this each time you run configure, because configure regenerates `config.h'.)
The `sql_yacc.cc' file is generated from `sql_yacc.yy'. Normally the build process doesn't need to create `sql_yacc.cc', because MySQL comes with an already-generated copy. However, if you do need to re-create it, you might encounter this error:
```
"sql_yacc.yy", line xxx fatal: default action causes potential...
```
This is a sign that your version of yacc is deficient. You probably need to install bison (the GNU version of yacc) and use that instead.
If you need to debug mysqld or a MySQL client, run configure with the --with-debug option, then recompile and link your clients with the new client library. See section I.2 Debugging a MySQL client.

4.10 MIT-pthreads Notes

This section describes some of the issues involved in using MIT-pthreads.

Note that on Linux you should NOT use MIT-pthreads but install LinuxThreads! See section 4.12.5 Linux Notes (All Linux Versions).

If your system does not provide native thread support, you will need to build MySQL using the MIT-pthreads package. This includes older FreeBSD systems, SunOS 4.x, Solaris 2.4 and earlier, and some others. See section 4.2 Operating Systems Supported by MySQL.

On most systems, you can force MIT-pthreads to be used by running configure with the --with-mit-threads option:
```
shell> ./configure --with-mit-threads
```
Building in a non-source directory is not supported when using MIT-pthreads, because we want to minimize our changes to this code.
The checks that determine whether or not to use MIT-pthreads occur only during the part of the configuration process that deals with the server code. If you have configured the distribution using --without-server to build only the client code, clients will not know whether or not MIT-pthreads is being used and will use Unix socket connections by default. Because Unix sockets do not work under MIT-pthreads, this means you will need to use -h or --host when you run client programs.
When MySQL is compiled using MIT-pthreads, system locking is disabled by default for performance reasons. You can tell the server to use system locking with the --use-locking option.
Sometimes the pthread bind() command fails to bind to a socket without any error message (at least on Solaris). The result is that all connections to the server fail. For example:
```
shell> mysqladmin version
mysqladmin: connect to server at '' failed;
error: 'Can't connect to mysql server on localhost (146)'
```
The solution to this is to kill the mysqld server and restart it. This has only happened to us when we have forced the server down and done a restart immediately.
With MIT-pthreads, the sleep() system call isn't interruptible with SIGINT (break). This is only noticeable when you run mysqladmin --sleep. You must wait for the sleep() call to terminate before the interrupt is served and the process stops.

When linking, you may receive warning messages like these (at least on Solaris); they can be ignored:

ld: warning: symbol `_iob' has differing sizes:
    (file /my/local/pthreads/lib/libpthread.a(findfp.o) value=0x4;
file /usr/lib/libc.so value=0x140);
    /my/local/pthreads/lib/libpthread.a(findfp.o) definition taken
ld: warning: symbol `__iob' has differing sizes:
    (file /my/local/pthreads/lib/libpthread.a(findfp.o) value=0x4;
file /usr/lib/libc.so value=0x140);
    /my/local/pthreads/lib/libpthread.a(findfp.o) definition taken

Some other warnings also can be ignored:

implicit declaration of function `int strtoll(...)'
implicit declaration of function `int strtoul(...)'

We haven't gotten readline to work with MIT-pthreads. (This isn't needed, but may be interesting for someone.)

4.11 Perl Installation Comments

4.11.1 Installing Perl on Unix

Perl support for MySQL is provided by means of the DBI/DBD client interface. See section 24.2 MySQL Perl API. The Perl DBD/DBI client code requires Perl Version 5.004 or later. The interface will not work if you have an older version of Perl.

MySQL Perl support also requires that you've installed MySQL client programming support. If you installed MySQL from RPM files, client programs are in the client RPM, but client programming support is in the developer RPM. Make sure you've installed the latter RPM.

As of Version 3.22.8, Perl support is distributed separately from the main MySQL distribution. If you want to install Perl support, the files you will need can be obtained from http://www.mysql.com/Downloads/Contrib/.

The Perl distributions are provided as compressed tar archives and have names like `MODULE-VERSION.tar.gz', where MODULE is the module name and VERSION is the version number. You should get the Data-Dumper, DBI, and Msql-Mysql-modules distributions and install them in that order. The installation procedure is shown below. The example shown is for the Data-Dumper module, but the procedure is the same for all three distributions:

Unpack the distribution into the current directory:
```
shell> gunzip < Data-Dumper-VERSION.tar.gz | tar xvf -
```
This command creates a directory named `Data-Dumper-VERSION'.
Change into the top-level directory of the unpacked distribution:
```
shell> cd Data-Dumper-VERSION
```

Build the distribution and compile everything:

shell> perl Makefile.PL
shell> make
shell> make test
shell> make install

The make test command is important because it verifies that the module is working. Note that when you run that command during the Msql-Mysql-modules installation to exercise the interface code, the MySQL server must be running or the test will fail.

It is a good idea to rebuild and reinstall the Msql-Mysql-modules distribution whenever you install a new release of MySQL, particularly if you notice symptoms such as all your DBI scripts dumping core after you upgrade MySQL.

If you don't have the right to install Perl modules in the system directory or if you to install local Perl modules, the following reference may help you:

http://www.iserver.com/support/contrib/perl5/modules.html

Look under the heading Installing New Modules that Require Locally Installed Modules.

4.11.2 Installing ActiveState Perl on Windows

To install the MySQL DBD module with ActiveState Perl on Windows, you should do the following:

Get ActiveState Perl from http://www.activestate.com/Products/ActivePerl/index.html and install it.
Open a DOS shell.
If required, set the HTTP_proxy variable. For example, you might try:
```
set HTTP_proxy=my.proxy.com:3128
```
Start the PPM program:
```
C:\> c:\perl\bin\ppm.pl
```
If you have not already done so, install DBI:
```
ppm> install DBI
```

If this succeeds, run the following command:

install ftp://ftp.de.uu.net/pub/CPAN/authors/id/JWIED/DBD-mysql-1.2212.x86.ppd

The above should work at least with ActiveState Perl Version 5.6.

If you can't get the above to work, you should instead install the MyODBC driver and connect to MySQL server through ODBC:

use DBI;
$dbh= DBI->connect("DBI:ODBC:$dsn","$user","$password") ||
  die "Got error $DBI::errstr when connecting to $dsn\n";

4.11.3 Installing the MySQL Perl Distribution on Windows

The MySQL Perl distribution contains DBI, DBD:MySQL and DBD:ODBC.

Get the Perl distribution for Windows from http://www.mysql.com/download.html.
Unzip the distribution in C: so that you get a `C:\PERL' directory.
Add the directory `C:\PERL\BIN' to your path.
Add the directory `C:\PERL\BIN\MSWIN32-x86-thread' or `C:\PERL\BIN\MSWIN32-x86' to your path.
Test that perl works by executing perl -v in a DOS shell.

4.11.4 Problems Using the Perl `DBI`/`DBD` Interface

If Perl reports that it can't find the `../mysql/mysql.so' module, then the problem is probably that Perl can't locate the shared library `libmysqlclient.so'.

You can fix this by any of the following methods:

Compile the Msql-Mysql-modules distribution with perl Makefile.PL -static -config rather than perl Makefile.PL.
Copy libmysqlclient.so to the directory where your other shared libraries are located (probably `/usr/lib' or `/lib').
On Linux you can add the pathname of the directory where `libmysqlclient.so' is located to the `/etc/ld.so.conf' file.
Add the pathname of the directory where `libmysqlclient.so' is located to the LD_RUN_PATH environment variable.

If you get the following errors from DBD-mysql, you are probably using gcc (or using an old binary compiled with gcc):

/usr/bin/perl: can't resolve symbol '__moddi3'
/usr/bin/perl: can't resolve symbol '__divdi3'

Add -L/usr/lib/gcc-lib/... -lgcc to the link command when the `mysql.so' library gets built (check the output from make for `mysql.so' when you compile the Perl client). The -L option should specify the pathname of the directory where `libgcc.a' is located on your system.

Another cause of this problem may be that Perl and MySQL aren't both compiled with gcc. In this case, you can solve the mismatch by compiling both with gcc.

If you get the following error from Msql-Mysql-modules when you run the tests:

t/00base............install_driver(mysql) failed: Can't load '../blib/arch/auto/DBD/mysql/mysql.so' for module DBD::mysql: ../blib/arch/auto/DBD/mysql/mysql.so: undefined symbol: uncompress at /usr/lib/perl5/5.00503/i586-linux/DynaLoader.pm line 169.

it means that you need to include the compression library, -lz, to the link line. This can be doing the following change in the file `lib/DBD/mysql/Install.pm':

$sysliblist .= " -lm";

to

$sysliblist .= " -lm -lz";

After this, you MUST run 'make realclean' and then proceed with the installation from the beginning.

If you want to use the Perl module on a system that doesn't support dynamic linking (like SCO) you can generate a static version of Perl that includes DBI and DBD-mysql. The way this works is that you generate a version of Perl with the DBI code linked in and install it on top of your current Perl. Then you use that to build a version of Perl that additionally has the DBD code linked in, and install that.

On SCO, you must have the following environment variables set:

shell> LD_LIBRARY_PATH=/lib:/usr/lib:/usr/local/lib:/usr/progressive/lib
or
shell> LD_LIBRARY_PATH=/usr/lib:/lib:/usr/local/lib:/usr/ccs/lib:/usr/progressive/lib:/usr/skunk/lib
shell> LIBPATH=/usr/lib:/lib:/usr/local/lib:/usr/ccs/lib:/usr/progressive/lib:/usr/skunk/lib
shell> MANPATH=scohelp:/usr/man:/usr/local1/man:/usr/local/man:/usr/skunk/man:

First, create a Perl that includes a statically linked DBI by running these commands in the directory where your DBI distribution is located:

shell> perl Makefile.PL -static -config
shell> make
shell> make install
shell> make perl

Then you must install the new Perl. The output of make perl will indicate the exact make command you will need to execute to perform the installation. On SCO, this is make -f Makefile.aperl inst_perl MAP_TARGET=perl.

Next, use the just-created Perl to create another Perl that also includes a statically-linked DBD::mysql by running these commands in the directory where your Msql-Mysql-modules distribution is located:

shell> perl Makefile.PL -static -config
shell> make
shell> make install
shell> make perl

Finally, you should install this new Perl. Again, the output of make perl indicates the command to use.

4.12 System-specific Issues

The following sections indicate some of the issues that have been observed to occur on particular systems when installing MySQL from a source distribution.

4.12.1 Solaris Notes

On Solaris, you may run into trouble even before you get the MySQL distribution unpacked! Solaris tar can't handle long file names, so you may see an error like this when you unpack MySQL:

x mysql-3.22.12-beta/bench/Results/ATIS-mysql_odbc-NT_4.0-cmp-db2,informix,ms-sql,mysql,oracle,solid,sybase, 0 bytes, 0 tape blocks
tar: directory checksum error

In this case, you must use GNU tar (gtar) to unpack the distribution. You can find a precompiled copy for Solaris at http://www.mysql.com/Downloads/.

Sun native threads work only on Solaris 2.5 and higher. For Version 2.4 and earlier, MySQL will automatically use MIT-pthreads. See section 4.10 MIT-pthreads Notes.

If you get the following error from configure:

checking for restartable system calls... configure: error can not run test
programs while cross compiling

This means that you have something wrong with your compiler installation! In this case you should upgrade your compiler to a newer version. You may also be able to solve this problem by inserting the following row into the `config.cache' file:

ac_cv_sys_restartable_syscalls=${ac_cv_sys_restartable_syscalls='no'}

If you are using Solaris on a SPARC, the recommended compiler is gcc 2.95.2. You can find this at http://gcc.gnu.org/. Note that egs 1.1.1 and gcc 2.8.1 don't work reliably on SPARC!

The recommended configure line when using gcc 2.95.2 is:

CC=gcc CFLAGS="-O3" \
CXX=gcc CXXFLAGS="-O3 -felide-constructors -fno-exceptions -fno-rtti" \
./configure --prefix=/usr/local/mysql --with-low-memory --enable-assembler

If you have a ultra sparc, you can get 4 % more performance by adding "-mcpu=v8 -Wa,-xarch=v8plusa" to CFLAGS and CXXFLAGS.

If you have the Sun Workshop (SunPro) 4.2 (or newer) compiler, you can run configure like this:

CC=cc CFLAGS="-Xa -fast -xO4 -native -xstrconst -mt" \
CXX=CC CXXFLAGS="-noex -xO4 -mt" \
./configure --prefix=/usr/local/mysql --enable-assembler

You may also have to edit the configure script to change this line:

#if !defined(__STDC__) || __STDC__ != 1

to this:

#if !defined(__STDC__)

If you turn on __STDC__ with the -Xc option, the Sun compiler can't compile with the Solaris `pthread.h' header file. This is a Sun bug (broken compiler or broken include file).

If mysqld issues the error message shown below when you run it, you have tried to compile MySQL with the Sun compiler without enabling the multi-thread option (-mt):

libc internal error: _rmutex_unlock: rmutex not held

Add -mt to CFLAGS and CXXFLAGS and try again.

If you get the following error when compiling MySQL with gcc, it means that your gcc is not configured for your version of Solaris:

shell> gcc -O3 -g -O2 -DDBUG_OFF  -o thr_alarm ...
./thr_alarm.c: In function `signal_hand':
./thr_alarm.c:556: too many arguments to function `sigwait'

The proper thing to do in this case is to get the newest version of gcc and compile it with your current gcc compiler! At least for Solaris 2.5, almost all binary versions of gcc have old, unusable include files that will break all programs that use threads (and possibly other programs)!

Solaris doesn't provide static versions of all system libraries (libpthreads and libdl), so you can't compile MySQL with --static. If you try to do so, you will get the error:

ld: fatal: library -ldl: not found

If too many processes try to connect very rapidly to mysqld, you will see this error in the MySQL log:

Error in accept: Protocol error

You might try starting the server with the --set-variable back_log=50 option as a workaround for this. See section 4.16.4 mysqld Command-line Options.

If you are linking your own MySQL client, you might get the following error when you try to execute it:

ld.so.1: ./my: fatal: libmysqlclient.so.#: open failed: No such file or directory

The problem can be avoided by one of the following methods:

Link the client with the following flag (instead of -Lpath): -Wl,r/full-path-to-libmysqlclient.so.
Copy `libmysqclient.so' to `/usr/lib'.
Add the pathname of the directory where `libmysqlclient.so' is located to the LD_RUN_PATH environment variable before running your client.

When using the --with-libwrap configure option, you must also include the libraries that `libwrap.a' needs:

--with-libwrap="/opt/NUtcpwrapper-7.6/lib/libwrap.a -lnsl -lsocket

If you have problems with configure trying to link with -lz and you don't have zlib installed, you have two options:

If you want to be able to use the compressed communication protocol, you need to get and install zlib from ftp.gnu.org.
Configure with --with-named-z-libs=no.

If you are using gcc and have problems with loading UDF functions into MySQL, try adding -lgcc to the link line for the UDF function.

If you would like MySQL to start automatically, you can copy `support-files/mysql.server' to `/etc/init.d' and create a symbolic link to it named `/etc/rc3.d/S99mysql.server'.

4.12.2 Solaris 2.7/2.8 Notes

You can normally use a Solaris 2.6 binary on Solaris 2.7 and 2.8. Most of the Solaris 2.6 issues also apply for Solaris 2.7 and 2.8.

Note that MySQL Version 3.23.4 and above should be able to autodetect new versions of Solaris and enable workarounds for the following problems!

Solaris 2.7 / 2.8 has some bugs in the include files. You may see the following error when you use gcc:

/usr/include/widec.h:42: warning: `getwc' redefined
/usr/include/wchar.h:326: warning: this is the location of the previous
definition

If this occurs, you can do the following to fix the problem:

Copy /usr/include/widec.h to .../lib/gcc-lib/os/gcc-version/include and change line 41 from:

#if     !defined(lint) && !defined(__lint)

to

#if     !defined(lint) && !defined(__lint) && !defined(getwc)

Alternatively, you can edit `/usr/include/widec.h' directly. Either way, after you make the fix, you should remove `config.cache' and run configure again!

If you get errors like this when you run make, it's because configure didn't detect the `curses.h' file (probably because of the error in `/usr/include/widec.h'):

In file included from mysql.cc:50:
/usr/include/term.h:1060: syntax error before `,'
/usr/include/term.h:1081: syntax error before `;'

The solution to this is to do one of the following:

Configure with CFLAGS=-DHAVE_CURSES_H CXXFLAGS=-DHAVE_CURSES_H ./configure.
Edit `/usr/include/widec.h' as indicted above and rerun configure.
Remove the #define HAVE_TERM line from `config.h' file and run make again.

If you get a problem that your linker can't find -lz when linking your client program, the problem is probably that your `libz.so' file is installed in `/usr/local/lib'. You can fix this by one of the following methods:

Add `/usr/local/lib' to LD_LIBRARY_PATH.
Add a link to `libz.so' from `/lib'.
If you are using Solaris 8, you can install the optional zlib from your Solaris 8 CD distribution.
Configure MySQL with the --with-named-z-libs=no option.

4.12.3 Solaris x86 Notes

If you are using gcc or egcs on Solaris x86 and you experience problems with core dumps under load, you should use the following configure command:

CC=gcc CFLAGS="-O3 -fomit-frame-pointer -DHAVE_CURSES_H" \
CXX=gcc \
CXXFLAGS="-O3 -fomit-frame-pointer -felide-constructors -fno-exceptions -fno-rtti -DHAVE_CURSES_H" \
./configure --prefix=/usr/local/mysql

This will avoid problems with the libstdc++ library and with C++ exceptions.

If this doesn't help, you should compile a debug version and run it with a trace file or under gdb. See section I.1 Debugging a MySQL server.

4.12.4 SunOS 4 Notes

On SunOS 4, MIT-pthreads is needed to compile MySQL, which in turn means you will need GNU make.

Some SunOS 4 systems have problems with dynamic libraries and libtool. You can use the following configure line to avoid this problem:

shell> ./configure --disable-shared --with-mysqld-ldflags=-all-static

When compiling readline, you may get warnings about duplicate defines. These may be ignored.

When compiling mysqld, there will be some implicit declaration of function warnings. These may be ignored.

4.12.5 Linux Notes (All Linux Versions)

The notes below regarding glibc apply only to the situation when you build MySQL yourself. If you are running Linux on an x86 machine, in most cases it is much better for you to just use our binary. We link our binaries against the best patched version of glibc we can come up with and with the best compiler options, in an attempt to make it suitable for a high-load server. So if you read the text below, and are in doubt about what you should do, try our binary first to see if it meets your needs, and worry about your own build only after you have discovered that our binary is not good enough. In that case, we would appreciate a note about it, so we can build a better binary next time. For a typical user, even for setups with a lot of concurrent connections and/or tables exceeding 2GB limit, our binary in most cases is the best choice.

MySQL uses LinuxThreads on Linux. If you are using an old Linux version that doesn't have glibc2, you must install LinuxThreads before trying to compile MySQL. You can get LinuxThreads at http://www.mysql.com/Downloads/Linux.

Note that glibc versions before and including Version 2.1.1 have a fatal bug in pthread_mutex_timedwait handling, which is used when you do INSERT DELAYED. We recommend you to not use INSERT DELAYED before upgrading glibc.

If you plan to have 1000+ concurrent connections, you will need to make some changes to LinuxThreads, recompile it, and relink MySQL against the new `libpthread.a'. Increase PTHREAD_THREADS_MAX in `sysdeps/unix/sysv/linux/bits/local_lim.h' to 4096 and decrease STACK_SIZE in `linuxthreads/internals.h' to 256 KB. The paths are relative to the root of glibc Note that MySQL will not be stable with around 600-1000 connections if STACK_SIZE is the default of 2 MB.

The STACK_SIZE constant in LinuxThreads controls the spacing of thread stacks in the address space. It needs to be large enough so that there will be plenty of room for the stack of each individual thread, but small enough to keep the stack of some thread from running into the global mysqld data. Unfortunately, the Linux implementation of mmap(), as we have experimentally discovered, will successfully unmap an already mapped region if you ask it to map out an address already in use, zeroing out the data on the entire page, instead of returning an error. So, the safety of mysqld or any other threaded application depends on the "gentleman" behaviour of the code that creates threads. The user must take measures to make sure the number of running threads at any time is sufficiently low for thread stacks to stay away from the global heap. With mysqld, you should enforce this "gentleman" behaviour by setting a reasonable value for the max_connections variable.

If you build MySQL yourself and do not what to mess with patching LinuxThreads, you should set max_connections to a value no higher than 500. It should be even less if you have a large key buffer, large heap tables, or some other things that make mysqld allocate a lot of memory or if you are running a 2.2 kernel with a 2GB patch. If you are using our binary or RPM version 3.23.25 or later, you can safely set max_connections at 1500, assuming no large key buffer or heap tables with lots of data. The more you reduce STACK_SIZE in LinuxThreads the more threads you can safely create. We recommend the values between 128K and 256K.

If you use a lot of concurrent connections, you may suffer from a "feature" in the 2.2 kernel that penalizes a process for forking or cloning a child in an attempt to prevent a fork bomb attack. This will cause MySQL not to scale well as you increase the number of concurrent clients. On single CPU systems, we have seen this manifested in a very slow thread creation, which means it may take a long time to connect to MySQL (as long as 1 minute), and it may take just as long to shut it down. On multiple CPU systems, we have observed a gradual drop in query speed as the number of clients increases. In the process of trying to find a solution, we have received a kernel patch from one of our users, who claimed it made a lot of difference for his site. The patch is available here (http://www.mysql.com/Downloads/Patches/linux-fork.patch). We have now done rather extensive testing of this patch on both development and production systems. It has significantly improved MySQL performance without causing any problems and we now recommend it to our users who are still running high-load servers on 2.2 kernels. This issue has been fixed in the 2.4 kernel, so if you are not satisfied with the current performance of your system, rather than patching your 2.2 kernel, it might be easier to just upgrade to 2.4, which will also give you a nice SMP boost in addition to fixing this fairness bug.

We have tested MySQL on the 2.4 kernel on a 2 CPU machine and found MySQL scales MUCH better - there was virtually no slowdown on query throughput all the way up to 1000 clients, and MySQL scaling factor ( computed as the ratio of maximum throughput to the throughput with one client) was 180%. We have observed similar results on a 4-CPU system - virtually no slowdown as the number of clients was increased up to 1000, and 300% scaling factor. So for a high-load SMP server we would definitely recommend the 2.4 kernel at this point. We have discovered that it is essential to run mysqld process with the highest possible priority on the 2.4 kernel to achieve maximum performance. This can be done by adding renice -20 $$ command to safe_mysqld. In our testing on a 4-CPU machine, increasing the priority gave 60% increase in throughput with 400 clients.

We are currently also trying to collect more info on how well MySQL performs on 2.4 kernel on 4-way and 8-way systems. If you have access such a system and have done some benchmarks, please send a mail to docs@mysql.com with the results - we will include them in the manual.

There is another issue that greatly hurts MySQL performance, especially on SMP systems. The implementation of mutex in LinuxThreads in glibc-2.1 is very bad for programs with many threads that only hold the mutex for a short time. On an SMP system, ironic as it is, if you link MySQL against unmodified LinuxThreads, removing processors from the machine improves MySQL performance in many cases. We have made a patch available for glibc 2.1.3, linuxthreads-2.1-patch to correct this behaviour.

With glibc-2.2.2 MySQL version 3.23.36 will use the adaptive mutex, which is much better than even the patched one in glibc-2.1.3. Be warned, however, that under some conditions, the current mutex code in glibc-2.2.2 overspins, which hurts MySQL performance. The chance of this condition can be reduced by renicing mysqld process to the highest priority. We have also been able to correct the overspin behaviour with a patch, available here. It combines the correction of overspin, maximum number of threads, and stack spacing all in one. You will need to apply it in the linuxthreads directory with patch -p0 </tmp/linuxthreads-2.2.2.patch. We hope it will be included in some form in to the future releases of glibc-2.2. In any case, if you link against glibc-2.2.2 you still need to correct STACK_SIZE and PTHREAD_THREADS_MAX. We hope that the defaults will be corrected to some more acceptable values for high-load MySQL setup in the future, so that your own build can be reduced to ./configure; make; make install.

We recommend that you use the above patches to build a special static version of libpthread.a and use it only for statically linking against MySQL. We know that the patches are safe for MySQL and significantly improve its performance, but we cannot say anything about other applications. If you link other applications against the patched version of the library, or build a patched shared version and install it on your system, you are doing it at your own risk with regard to other applications that depend on LinuxThreads.

If you experience any strange problems during the installation of MySQL, or with some common utilties hanging, it is very likely that they are either library or compiler related. If this is the case, using our binary will resolve them.

One known problem with the binary distribution is that with older Linux systems that use libc (like RedHat 4.x or Slackware), you will get some non-fatal problems with hostname resolution. See section 4.6.3.1 Linux Notes for Binary Distributions.

When using LinuxThreads you will see a minimum of three processes running. These are in fact threads. There will be one thread for the LinuxThreads manager, one thread to handle connections, and one thread to handle alarms and signals.

Note that the Linux kernel and the LinuxThread library can by default only have 1024 threads. This means that you can only have up to 1021 connections to MySQL on an unpatched system. The page http://www.volano.com/linuxnotes.html contains information how to go around this limit.

If you see a dead mysqld daemon process with ps, this usually means that you have found a bug in MySQL or you have a corrupted table. See section 21.2 What to Do if MySQL Keeps Crashing.

To get a core dump on Linux if mysqld dies with a SIGSEGV signal, you can start mysqld with the --core-file option. Note that you also probably need to raise the core file size by adding ulimit -c 1000000 to safe_mysqld or starting safe_mysqld with --core-file-sizes=1000000. See section 15.3 safe_mysqld, the wrapper around mysqld.

If you are linking your own MySQL client and get the error:

ld.so.1: ./my: fatal: libmysqlclient.so.4: open failed: No such file or directory

When executing them, the problem can be avoided by one of the following methods:

Link the client with the following flag (instead of -Lpath): -Wl,r/path-libmysqlclient.so.
Copy libmysqclient.so to `/usr/lib'.
Add the pathname of the directory where libmysqlclient.so is located to the LD_RUN_PATH environment variable before running your client.

If you are using the Fujitsu compiler (fcc / FCC) you will have some problems compiling MySQL because the Linux header files are very gcc oriented.

The following configure line should work with fcc/FCC:

CC=fcc CFLAGS="-O -K fast -K lib -K omitfp -Kpreex -D_GNU_SOURCE -DCONST=const -DNO_STRTOLL_PROTO" CXX=FCC CXXFLAGS="-O -K fast -K lib  -K omitfp -K preex --no_exceptions --no_rtti -D_GNU_SOURCE -DCONST=const -Dalloca=__builtin_alloca -DNO_STRTOLL_PROTO '-D_EXTERN_INLINE=static __inline'" ./configure --prefix=/usr/local/mysql --enable-assembler --with-mysqld-ldflags=-all-static --disable-shared --with-low-memory

4.12.5.1 Linux-x86 Notes

MySQL requires libc Version 5.4.12 or newer. It's known to work with libc 5.4.46. glibc Version 2.0.6 and later should also work. There have been some problems with the glibc RPMs from RedHat, so if you have problems, check whether or not there are any updates! The glibc 2.0.7-19 and 2.0.7-29 RPMs are known to work.

On some older Linux distributions, configure may produce an error like this:

Syntax error in sched.h. Change _P to __P in the /usr/include/sched.h file.
See the Installation chapter in the Reference Manual.

Just do what the error message says and add an extra underscore to the _P macro that has only one underscore, then try again.

You may get some warnings when compiling; those shown below can be ignored:

mysqld.cc -o objs-thread/mysqld.o
mysqld.cc: In function `void init_signals()':
mysqld.cc:315: warning: assignment of negative value `-1' to `long unsigned int'
mysqld.cc: In function `void * signal_hand(void *)':
mysqld.cc:346: warning: assignment of negative value `-1' to `long unsigned int'

In Debian GNU/Linux, if you want MySQL to start automatically when the system boots, do the following:

shell> cp support-files/mysql.server /etc/init.d/mysql.server
shell> /usr/sbin/update-rc.d mysql.server defaults 99

mysql.server can be found in the `share/mysql' directory under the MySQL installation directory or in the `support-files' directory of the MySQL source tree.

If mysqld always core dumps when it starts up, the problem may be that you have an old `/lib/libc.a'. Try renaming it, then remove `sql/mysqld' and do a new make install and try again. This problem has been reported on some Slackware installations. RedHat Version 5.0 also has a similar problem with some new glibc versions. See section 4.12.5.2 RedHat Version 5.0 Notes.

If you get the following error when linking mysqld, it means that your `libg++.a' is not installed correctly:

/usr/lib/libc.a(putc.o): In function `_IO_putc':
putc.o(.text+0x0): multiple definition of `_IO_putc'

You can avoid using `libg++.a' by running configure like this:

shell> CXX=gcc ./configure

4.12.5.2 RedHat Version 5.0 Notes

If you have any problems with MySQL on RedHat, you should start by upgrading glibc to the newest possible version!

If you install all the official RedHat patches (including glibc-2.0.7-19 and glibc-devel-2.0.7-19), both the binary and source distributions of MySQL should work without any trouble!

The updates are needed because there is a bug in glibc 2.0.5 in how pthread_key_create variables are freed. With glibc 2.0.5, you must use a statically linked MySQL binary distribution. If you want to compile from source, you must install the corrected version of LinuxThreads from http://www.mysql.com/Downloads/Linux or upgrade your glibc.

If you have an incorrect version of glibc or LinuxThreads, the symptom is that mysqld crashes after each connection. For example, mysqladmin version will crash mysqld when it finishes!

Another symptom of incorrect libraries is that mysqld crashes at once when it starts. On some Linux systems, this can be fixed by configuring like this:

shell> ./configure --with-mysqld-ldflags=-all-static

On Redhat Version 5.0, the easy way out is to install the glibc 2.0.7-19 RPM and run configure without the --with-mysqld-ldflags=-all-static option.

For the source distribution of glibc 2.0.7, a patch that is easy to apply and is tested with MySQL may be found at:

http://www.mysql.com/Download/Linux/glibc-2.0.7-total-patch.tar.gz

If you experience crashes like these when you build MySQL, you can always download the newest binary version of MySQL. This is statically-linked to avoid library conflicts and should work on all Linux systems!

MySQL comes with an internal debugger that can generate trace files with a lot of information that can be used to find and solve a wide range of different problems. See section I.1 Debugging a MySQL server.

4.12.5.3 RedHat Version 5.1 notes

The glibc of RedHat Version 5.1 (glibc 2.0.7-13) has a memory leak, so to get a stable MySQL version, you must upgrade glibc, to 2.0.7-19, downgrade glibc or use a binary version of mysqld. If you don't do this, you will encounter memory problems (out of memory, etc.). The most common error in this case is:

Can't create a new thread (errno 11). If you are not out of available
memory, you can consult the manual for any possible OS dependent bug

After you have upgraded to glibc 2.0.7-19, you can configure MySQL with dynamic linking (the default), but you cannot run configure with the --with-mysqld-ldflags=-all-static option until you have installed glibc 2.0.7-19 from source!

You can check which version of glibc you have with rpm -q glibc.

Another reason for the above error is if you try to use more threads than your Linux kernel is configured for. In this case you should raise the limits in `include/linux/tasks.h' and recompile your kernel!

4.12.5.4 Linux-SPARC Notes

In some implementations, readdir_r() is broken. The symptom is that SHOW DATABASES always returns an empty set. This can be fixed by removing HAVE_READDIR_R from `config.h' after configuring and before compiling.

Some problems will require patching your Linux installation. The patch can be found at http://www.mysql.com/Downloads/patches/Linux-sparc-2.0.30.diff. This patch is against the Linux distribution `sparclinux-2.0.30.tar.gz' that is available at vger.rutgers.edu (a version of Linux that was never merged with the official 2.0.30). You must also install LinuxThreads Version 0.6 or newer.

4.12.5.5 Linux-Alpha Notes

MySQL Version 3.23.12 is the first MySQL version that is tested on Linux-Alpha. If you plan to use MySQL on Linux-Alpha, you should ensure that you have this version or newer.

We have tested MySQL on Alpha with our benchmarks and test suite, and it appears to work nicely. The main thing we haven't yet had time to test is how things works with many concurrent users.

When we compiled the standard MySQL binary we are using SuSE 6.4, kernel 2.2.13-SMP, Compaq C compiler (V6.2-504) and Compaq C++ compiler (V6.3-005) on a Comaq DS20 machine with an Alpha EV6 processor.

You can find the above compilers at http://www.support.compaq.com/alpha-tools). By using these compilers, instead of gcc, we get about 9-14 % better performance with MySQL.

Note that the configure line optimized the binary for the current CPU; This means you can only use our binary if you have an Alpha EV6 processor. We also compile statically to avoid library problems.

CC=ccc CFLAGS="-fast" CXX=cxx CXXFLAGS="-fast -noexceptions -nortti" ./configure --prefix=/usr/local/mysql --disable-shared --with-extra-charsets=complex --enable-thread-safe-client --with-mysqld-ldflags=-non_shared --with-client-ldflags=-non_shared

If you want to use egcs the following configure line worked for us:

CFLAGS="-O3 -fomit-frame-pointer" CXX=gcc CXXFLAGS="-O3 -fomit-frame-pointer -felide-constructors -fno-exceptions -fno-rtti" ./configure --prefix=/usr/local/mysql --disable-shared

Some known problems when running MySQL on Linux-Alpha:

Debugging threaded applications like MySQL will not work with gdb 4.18. You should download and use gdb 5.0 instead!
If you try linking mysqld statically when using gcc, the resulting image will core dump at start. In other words, DON'T use --with-mysqld-ldflags=-all-static with gcc.

4.12.5.6 MkLinux Notes

MySQL should work on MkLinux with the newest glibc package (tested with glibc 2.0.7).

4.12.5.7 Qube2 Linux Notes

To get MySQL to work on Qube2, (Linux Mips), you need the newest glibc libraries (glibc-2.0.7-29C2 is known to work). You must also use the egcs C++ compiler (egcs-1.0.2-9, gcc 2.95.2 or newer).

4.12.5.8 Linux IA64 Notes

To get MySQL to compile on Linux Ia64, we had to do the following (we assume that this will be easier when next gcc version for ia64 is released).

Using gcc-2.9-final:

CFLAGS="-O2" CXX=gcc CXXFLAGS="-O2 -felide-constructors -fno-exceptions -fno-rtti" ./configure --prefix=/usr/local/mysql --enable-assembler --with-mysqld-ldflags=-all-static --disable-shared --with-extra-charsets=complex

After make you will get an error that sql/opt_range.cc will not compile (internal compiler error). To fix this, go to the sql directory and type make again. Copy the compile line, but change -O2 to -O0. The file should now compile.

Now you can do:

cd ..
make
make_install

and mysqld should be ready to run.

4.12.6 Alpha-DEC-UNIX Notes (Tru64)

If you are using egcs 1.1.2 on Digital Unix, you should upgrade to gcc 2.95.2, as egcs on DEC has some serious bugs!

When compiling threaded programs under Digital Unix, the documentation recommends using the -pthread option for cc and cxx and the libraries -lmach -lexc (in addition to -lpthread). You should run configure something like this:

CC="cc -pthread" CXX="cxx -pthread -O" \
./configure --with-named-thread-libs="-lpthread -lmach -lexc -lc"

When compiling mysqld, you may see a couple of warnings like this:

mysqld.cc: In function void handle_connections()':
mysqld.cc:626: passing long unsigned int *' as argument 3 of
accept(int,sockadddr *, int *)'

You can safely ignore these warnings. They occur because configure can detect only errors, not warnings.

If you start the server directly from the command line, you may have problems with it dying when you log out. (When you log out, your outstanding processes receive a SIGHUP signal.) If so, try starting the server like this:

shell> nohup mysqld [options] &

nohup causes the command following it to ignore any SIGHUP signal sent from the terminal. Alternatively, start the server by running safe_mysqld, which invokes mysqld using nohup for you. See section 15.3 safe_mysqld, the wrapper around mysqld.

If you get a problem when compiling mysys/get_opt.c, just remove the line #define _NO_PROTO from the start of that file!

If you are using Compac's CC compiler, the following configure line should work:

CC="cc -pthread"
CFLAGS="-O4 -ansi_alias -ansi_args -fast -inline speed -speculate all -arch host"
CXX="cxx -pthread"
CXXFLAGS="-O4 -ansi_alias -ansi_args -fast -inline speed -speculate all -arch host"
export CC CFLAGS CXX CXXFLAGS
./configure \
--prefix=/usr/local/mysql \
--with-low-memory \
--enable-large-files \
--enable-shared=yes \
--with-named-thread-libs="-lpthread -lmach -lexc -lc"
gnumake

If you get a problem with libtool, when compiling with shared libraries as above, when linking mysql, you should be able to get around this by issuing:

cd mysql
/bin/sh ../libtool --mode=link cxx -pthread  -O3 -DDBUG_OFF \
-O4 -ansi_alias -ansi_args -fast -inline speed \
-speculate all \ -arch host  -DUNDEF_HAVE_GETHOSTBYNAME_R \
-o mysql  mysql.o readline.o sql_string.o completion_hash.o \
../readline/libreadline.a -lcurses \
../libmysql/.libs/libmysqlclient.so  -lm
cd ..
gnumake
gnumake install
scripts/mysql_install_db

4.12.7 Alpha-DEC-OSF1 Notes

If you have problems compiling and have DEC CC and gcc installed, try running configure like this:

CC=cc CFLAGS=-O CXX=gcc CXXFLAGS=-O3 \
./configure --prefix=/usr/local/mysql

If you get problems with the `c_asm.h' file, you can create and use a 'dummy' `c_asm.h' file with:

touch include/c_asm.h
CC=gcc CFLAGS=-I./include \
CXX=gcc CXXFLAGS=-O3 \
./configure --prefix=/usr/local/mysql

Note that the following problems with the ld program can be fixed by downloading the latest DEC (Compaq) patch kit from: http://ftp.support.compaq.com/public/unix/.

On OSF1 V4.0D and compiler "DEC C V5.6-071 on Digital Unix V4.0 (Rev. 878)" the compiler had some strange behavior (undefined asm symbols). /bin/ld also appears to be broken (problems with _exit undefined errors occuring while linking mysqld). On this system, we have managed to compile MySQL with the following configure line, after replacing /bin/ld with the version from OSF 4.0C:

CC=gcc CXX=gcc CXXFLAGS=-O3 ./configure --prefix=/usr/local/mysql

With the Digital compiler "C++ V6.1-029", the following should work:

CC=cc -pthread
CFLAGS=-O4 -ansi_alias -ansi_args -fast -inline speed -speculate all -arch host
CXX=cxx -pthread
CXXFLAGS=-O4 -ansi_alias -ansi_args -fast -inline speed -speculate all -arch host -noexceptions -nortti
export CC CFLAGS CXX CXXFLAGS
./configure --prefix=/usr/mysql/mysql --with-mysqld-ldflags=-all-static --disable-shared --with-named-thread-libs="-lmach -lexc -lc"

In some versions of OSF1, the alloca() function is broken. Fix this by removing the line in `config.h' that defines 'HAVE_ALLOCA'.

The alloca() function also may have an incorrect prototype in /usr/include/alloca.h. This warning resulting from this can be ignored.

configure will use the following thread libraries automatically: --with-named-thread-libs="-lpthread -lmach -lexc -lc".

When using gcc, you can also try running configure like this:

shell> CFLAGS=-D_PTHREAD_USE_D4 CXX=gcc CXXFLAGS=-O3 ./configure ....

If you have problems with signals (MySQL dies unexpectedly under high load), you may have found an OS bug with threads and signals. In this case you can tell MySQL not to use signals by configuring with:

shell> CFLAGS=-DDONT_USE_THR_ALARM \
       CXXFLAGS=-DDONT_USE_THR_ALARM \
       ./configure ...

This doesn't affect the performance of MySQL, but has the side effect that you can't kill clients that are ``sleeping'' on a connection with mysqladmin kill or mysqladmin shutdown. Instead, the client will die when it issues its next command.

With gcc 2.95.2, you will probably run into the following compile error:

sql_acl.cc:1456: Internal compiler error in `scan_region', at except.c:2566
Please submit a full bug report.

To fix this you should change to the sql directory and do a ``cut and paste'' of the last gcc line, but change -O3 to -O0 (or add -O0 immediately after gcc if you don't have any -O option on your compile line.) After this is done you can just change back to the top-level directly and run make again.

4.12.8 SGI-Irix Notes

If you are using Irix Version 6.5.3 or newer mysqld will only be able to create threads if you run it as a user with CAP_SCHED_MGT privileges (like root) or give the mysqld server this privilege with the following shell command:

shell> chcap "CAP_SCHED_MGT+epi" /opt/mysql/libexec/mysqld

You may have to undefine some things in `config.h' after running configure and before compiling.

In some Irix implementations, the alloca() function is broken. If the mysqld server dies on some SELECT statements, remove the lines from `config.h' that define HAVE_ALLOC and HAVE_ALLOCA_H. If mysqladmin create doesn't work, remove the line from `config.h' that defines HAVE_READDIR_R. You may have to remove the HAVE_TERM_H line as well.

SGI recommends that you install all of the patches on this page as a set: http://support.sgi.com/surfzone/patches/patchset/6.2_indigo.rps.html

At the very minimum, you should install the latest kernel rollup, the latest rld rollup, and the latest libc rollup.

You definitely need all the POSIX patches on this page, for pthreads support:

http://support.sgi.com/surfzone/patches/patchset/6.2_posix.rps.html

If you get the something like the following error when compiling `mysql.cc':

"/usr/include/curses.h", line 82: error(1084): invalid combination of type

Type the following in the top-level directory of your MySQL source tree:

shell> extra/replace bool curses_bool < /usr/include/curses.h > include/curses.h
shell> make

There have also been reports of scheduling problems. If only one thread is running, things go slow. Avoid this by starting another client. This may lead to a 2-to-10-fold increase in execution speed thereafter for the other thread. This is a poorly understood problem with Irix threads; you may have to improvise to find solutions until this can be fixed.

If you are compiling with gcc, you can use the following configure command:

CC=gcc CXX=gcc CXXFLAGS=-O3 \
./configure --prefix=/usr/local/mysql --with-thread-safe-client --with-named-thread-libs=-lpthread

4.12.9 FreeBSD Notes

FreeBSD 3.x is recommended for running MySQL since the thread package is much more integrated.

The easiest and therefor the preferred way to install is to use the mysql-server and mysql-client ports available on http://www.freebsd.org.

Using these gives you:

A working MySQL with all optimizations known to work on your version of FreeBSD enabled.
Automatic configuration and build.
Startup scripts installed in /usr/local/etc/rc.d.
Ability to see which files that are installed with pkg_info -L. And to remove them all with pkg_delete if you no longer want MySQL on that machine.

It is reccomended you use MIT-pthreads on FreeBSD 2.x and native threads on Versions 3 and up. It is possible to run with native threads on some late 2.2.x versions but you may encounter problems shutting down mysqld.

The MYSQL Makefiles require GNU make (gmake) to work. If you want to compile MYSQL you need to install GNU make first.

Be sure to have your name resolver setup correct. Otherwise you may experience resolver delays or failures when connecting to mysqld.

Make sure that the localhost entry in the `/etc/hosts' file is correct (otherwise you will have problems connecting to the database). The `/etc/hosts' file should start with a line:

127.0.0.1       localhost localhost.your.domain

If you notice that configure will use MIT-pthreads, you should read the MIT-pthreads notes. See section 4.10 MIT-pthreads Notes.

If you get an error from make install that it can't find `/usr/include/pthreads', configure didn't detect that you need MIT-pthreads. This is fixed by executing these commands:

shell> rm config.cache
shell> ./configure --with-mit-threads

FreeBSD is also known to have a very low default file handle limit. See section 21.12 File Not Found. Uncomment the ulimit -n section in safe_mysqld or raise the limits for the mysqld user in /etc/login.conf (and rebuild it with cap_mkdb /etc/login.conf). Also be sure you set the appropriate class for this user in the password file if you are not using the default (use: chpass mysqld-user-name). See section 15.3 safe_mysqld, the wrapper around mysqld.

If you get problems with the current date in MySQL, setting the TZ variable will probably help. See section A Environment Variables.

To get a secure and stable system you should only use FreeBSD kernels that are marked -STABLE.

4.12.10 NetBSD notes

To compile on NetBSD you need GNU make. Otherwise the compile will crash when make tries to run lint on C++ files.

4.12.11 OpenBSD Notes

4.12.11.1 OpenBSD 2.5 Notes

On OpenBSD Version 2.5, you can compile MySQL with native threads with the following options:

CFLAGS=-pthread CXXFLAGS=-pthread ./configure --with-mit-threads=no

4.12.11.2 OpenBSD 2.8 Notes

Our users have reported that OpenBSD 2.8 has a threading bug which causes problems with MySQL. The OpenBSD Developers have fixed the problem, but as of January 25th, 2001, it's only available in the ``-current'' branch. The symptoms of this threading bug are: slow response, high load, high CPU usage, and crashes.

4.12.12 BSD/OS Notes

4.12.12.1 BSD/OS Version 2.x Notes

If you get the following error when compiling MySQL, your ulimit value for virtual memory is too low:

item_func.h: In method `Item_func_ge::Item_func_ge(const Item_func_ge &)':
item_func.h:28: virtual memory exhausted
make[2]: *** [item_func.o] Error 1

Try using ulimit -v 80000 and run make again. If this doesn't work and you are using bash, try switching to csh or sh; some BSDI users have reported problems with bash and ulimit.

If you are using gcc, you may also use have to use the --with-low-memory flag for configure to be able to compile `sql_yacc.cc'.

If you get problems with the current date in MySQL, setting the TZ variable will probably help. See section A Environment Variables.

4.12.12.2 BSD/OS Version 3.x Notes

Upgrade to BSD/OS Version 3.1. If that is not possible, install BSDIpatch M300-038.

Use the following command when configuring MySQL:

shell> env CXX=shlicc++ CC=shlicc2 \
       ./configure \
           --prefix=/usr/local/mysql \
           --localstatedir=/var/mysql \
           --without-perl \
           --with-unix-socket-path=/var/mysql/mysql.sock

The following is also known to work:

shell> env CC=gcc CXX=gcc CXXFLAGS=-O3 \
       ./configure \
           --prefix=/usr/local/mysql \
           --with-unix-socket-path=/var/mysql/mysql.sock

You can change the directory locations if you wish, or just use the defaults by not specifying any locations.

If you have problems with performance under heavy load, try using the --skip-thread-priority option to mysqld! This will run all threads with the same priority; on BSDI Version 3.1, this gives better performance (at least until BSDI fixes their thread scheduler).

If you get the error virtual memory exhausted while compiling, you should try using ulimit -v 80000 and run make again. If this doesn't work and you are using bash, try switching to csh or sh; some BSDI users have reported problems with bash and ulimit.

4.12.12.3 BSD/OS Version 4.x Notes

BSDI Version 4.x has some thread-related bugs. If you want to use MySQL on this, you should install all thread-related patches. At least M400-023 should be installed.

On some BSDI Version 4.x systems, you may get problems with shared libraries. The symptom is that you can't execute any client programs, for example, mysqladmin. In this case you need to reconfigure not to use shared libraries with the --disable-shared option to configure.

Some customers have had problems on BSDI 4.0.1 that the mysqld binary after a while can't open tables. This is because some library/system related bug causes mysqld to change current directory without asking for this!

The fix is to either upgrade to 3.23.34 or after running configure remove the line #define HAVE_REALPATH from config.h before running make.

Note that the above means that you can't symbolic link a database directories to another database directory or symbolic link a table to another database on BSDI! (Making a symbolic link to another disk is ok).

4.12.13 SCO Notes

The current port is tested only on a ``sco3.2v5.0.4'' and ``sco3.2v5.0.5'' system. There has also been a lot of progress on a port to ``sco 3.2v4.2''.

For the moment the recommended compiler on OpenServer is gcc 2.95.2. With this you should be able to compile MySQL with just:

CC=gcc CXX=gcc ./configure ... (options)

For OpenServer 5.0.X you need to use GDS in Skunkware 95 (95q4c). This is necessary because GNU gcc 2.7.2 in Skunkware 97 does not have GNU as. You can also use egcs 1.1.2 or newer http://www.egcs.com/. If you are using egcs 1.1.2 you have to execute the following command:
```
shell> cp -p /usr/include/pthread/stdtypes.h /usr/local/lib/gcc-lib/i386-pc-sco3.2v5.0.5/egcs-2.91.66/include/pthread/
```
You need the port of GCC 2.5.x for this product and the Development system. They are required on this version of SCO Unix. You cannot just use the GCC Dev system.
You should get the FSU Pthreads package and install it first. This can be found at http://www.cs.wustl.edu/~schmidt/ACE_wrappers/FSU-threads.tar.gz. You can also get a precompiled package from http://www.mysql.com/Downloads/SCO/FSU-threads-3.5c.tar.gz.
FSU Pthreads can be compiled with SCO Unix 4.2 with tcpip. Or OpenServer 3.0 or Open Desktop 3.0 (OS 3.0 ODT 3.0), with the SCO Development System installed using a good port of GCC 2.5.x ODT or OS 3.0 you will need a good port of GCC 2.5.x There are a lot of problems without a good port. The port for this product requires the SCO Unix Development system. Without it, you are missing the libraries and the linker that is needed.
To build FSU Pthreads on your system, do the following:
1. Run ./configure in the `threads/src' directory and select the SCO OpenServer option. This command copies `Makefile.SCO5' to `Makefile'.
2. Run make.
3. To install in the default `/usr/include' directory, login as root, then cd to the `thread/src' directory, and run make install.
Remember to use GNU make when making MySQL.
If you don't start safe_mysqld as root, you probably will get only the default 110 open files per process. mysqld will write a note about this in the log file.
With SCO 3.2V5.0.5, you should use FSU Pthreads version 3.5c or newer. You should also use gcc 2.95.2 or newer! The following configure command should work:
```
shell> ./configure --prefix=/usr/local/mysql --disable-shared
```
With SCO 3.2V4.2, you should use FSU Pthreads version 3.5c or newer. The following configure command should work:
```
shell> CFLAGS="-D_XOPEN_XPG4" CXX=gcc CXXFLAGS="-D_XOPEN_XPG4" \
       ./configure \
           --with-debug --prefix=/usr/local/mysql \
           --with-named-thread-libs="-lgthreads -lsocket -lgen -lgthreads" \
           --with-named-curses-libs="-lcurses"
```
You may get some problems with some include files. In this case, you can find new SCO-specific include files at http://www.mysql.com/Downloads/SCO/SCO-3.2v4.2-includes.tar.gz. You should unpack this file in the `include' directory of your MySQL source tree.

SCO development notes:

MySQL should automatically detect FSU Pthreads and link mysqld with -lgthreads -lsocket -lgthreads.
The SCO development libraries are re-entrant in FSU Pthreads. SCO claims that its libraries' functions are re-entrant, so they must be reentrant with FSU Pthreads. FSU Pthreads on OpenServer tries to use the SCO scheme to make re-entrant libraries.
FSU Pthreads (at least the version at http://www.mysql.com/) comes linked with GNU malloc. If you encounter problems with memory usage, make sure that `gmalloc.o' is included in `libgthreads.a' and `libgthreads.so'.
In FSU Pthreads, the following system calls are pthreads-aware: read(), write(), getmsg(), connect(), accept(), select(), and wait().

If you want to install DBI on SCO, you have to edit the `Makefile' in DBI-xxx and each subdirectory.

Note that the following assumes gcc 2.95.2 or newer:

OLD:                                  NEW:
CC = cc                               CC = gcc
CCCDLFLAGS = -KPIC -W1,-Bexport       CCCDLFLAGS = -fpic
CCDLFLAGS = -wl,-Bexport              CCDLFLAGS =

LD = ld                               LD = gcc -G -fpic
LDDLFLAGS = -G -L/usr/local/lib       LDDLFLAGS = -L/usr/local/lib
LDFLAGS = -belf -L/usr/local/lib      LDFLAGS = -L/usr/local/lib

LD = ld                               LD = gcc -G -fpic
OPTIMISE = -Od                        OPTIMISE = -O1

OLD:
CCCFLAGS = -belf -dy -w0 -U M_XENIX -DPERL_SCO5 -I/usr/local/include

NEW:
CCFLAGS = -U M_XENIX -DPERL_SCO5 -I/usr/local/include

This is because the Perl dynaloader will not load the DBI modules if they were compiled with icc or cc.

Perl works best when compiled with cc.

4.12.14 SCO Unixware Version 7.0 Notes

You must use a version of MySQL at least as recent as Version 3.22.13 because that version fixes some portability problems under Unixware.

We have been able to compile MySQL with the following configure command on Unixware Version 7.0.1:

CC=cc CXX=CC ./configure --prefix=/usr/local/mysql

If you want to use gcc, you must use gcc 2.95.2 or newer.

4.12.15 IBM-AIX notes

Automatic detection of xlC is missing from Autoconf, so a configure command something like this is needed when compiling MySQL (This example uses the IBM compiler):

export CC="xlc_r -ma -O3 -qstrict -qoptimize=3 -qmaxmem=8192 "
export CXX="xlC_r -ma -O3 -qstrict -qoptimize=3 -qmaxmem=8192"
export CFLAGS="-I /usr/local/include"
export LDLFAGS="-L /usr/local/lib"
export CPPFLAGS=$CFLAGS
export CXXFLAGS=$CFLAGS

./configure --prefix=/usr/local \
		--localstatedir=/var/mysql \
		--sysconfdir=/etc/mysql \
		--sbindir='/usr/local/bin' \
		--libexecdir='/usr/local/bin' \
		--enable-thread-safe-client \
		--enable-large-files

Above are the options used to compile the MySQL distribution that can be found at http://www-frec.bull.com/.

If you change the -O3 to -O2 in the above configure line, you must also remove the -qstrict option (this is a limitation in the IBM C compiler).

If you are using gcc or egcs to compile MySQL, you MUST use the -fno-exceptions flag, as the exception handling in gcc/egcs is not thread safe! (This is tested with egcs 1.1.). There are also some known problems with IBM's assembler, which may cause it to generate bad code when used with gcc.

We recommend the following configure line with egcs and gcc 2.95 on AIX:

CC="gcc -pipe -mcpu=power2 -Wa,-many" \
CXX="gcc -pipe -mcpu=power2 -Wa,-many" \
CXXFLAGS="-felide-constructors -fno-exceptions -fno-rtti" \
./configure --prefix=/usr/local/mysql --with-low-memory

The -Wa,-many is necessary for the compile to be successful. IBM is aware of this problem but is in to hurry to fix it because of the workaround available. We don't know if the -fno-exceptions is required with gcc 2.95, but as MySQL doesn't use exceptions and the above option generates faster code, we recommend that you should always use this option with egcs / gcc.

If you have problems with signals (MySQL dies unexpectedly under high load) you may have found an OS bug with threads and signals. In this case you can tell MySQL not to use signals by configuring with:

shell> CFLAGS=-DDONT_USE_THR_ALARM CXX=gcc \
       CXXFLAGS="-felide-constructors -fno-exceptions -fno-rtti -DDONT_USE_THR_ALARM" \
       ./configure --prefix=/usr/local/mysql --with-debug --with-low-memory

On some versions of AIX, linking with libbind.a makes getservbyname core dump. This is an AIX bug and should be reported to IBM.

4.12.16 HP-UX Version 10.20 Notes

There are a couple of small problems when compiling MySQL on HP-UX. We recommend that you use gcc instead of the HP-UX native compiler, because gcc produces better code!

We recommend using gcc 2.95 on HP-UX. Don't use high optimization flags (like -O6) as this may not be safe on HP-UX.

Note that MIT-pthreads can't be compiled with the HP-UX compiler because it can't compile .S (assembler) files.

The following configure line should work:

CFLAGS="-DHPUX -I/opt/dce/include" CXXFLAGS="-DHPUX -I/opt/dce/include -felide-constructors -fno-exceptions -fno-rtti" CXX=gcc ./configure --with-pthread --with-named-thread-libs='-ldce' --prefix=/usr/local/mysql --disable-shared

If you are compiling gcc 2.95 yourself, you should NOT link it with the DCE libraries (libdce.a or libcma.a) if you want to compile MySQL with MIT-pthreads. If you mix the DCE and MIT-pthreads packages you will get a mysqld to which you cannot connect. Remove the DCE libraries while you compile gcc 2.95!

4.12.17 HP-UX Version 11.x Notes

For HPUX Version 11.x we recommend MySQL Version 3.23.15 or later.

Because of some critical bugs in the standard HPUX libraries, one should install the following patches before trying to run MySQL on HPUX 11.0:

PHKL_22840 Streams cumulative
PHNE_22397 ARPA cumulative

This will solve a problem that one gets EWOULDBLOCK from recv() and EBADF from accept() in threaded applications.

If you are using gcc 2.95.1 on an unpatched HPUX 11.x system, you will get the error:

In file included from /usr/include/unistd.h:11,
                 from ../include/global.h:125,
                 from mysql_priv.h:15,
                 from item.cc:19:
/usr/include/sys/unistd.h:184: declaration of C function ...
/usr/include/sys/pthread.h:440: previous declaration ...
In file included from item.h:306,
                 from mysql_priv.h:158,
                 from item.cc:19:

The problem is that HP-UX doesn't define pthreads_atfork() consistently. It has conflicting prototypes in `/usr/include/sys/unistd.h':184 and `/usr/include/sys/pthread.h':440 (details below).

One solution is to copy `/usr/include/sys/unistd.h' into `mysql/include' and edit `unistd.h' and change it to match the definition in `pthread.h'. Here's the diff:

183,184c183,184
<      extern int pthread_atfork(void (*prepare)(), void (*parent)(),
<                                                void (*child)());
---
>      extern int pthread_atfork(void (*prepare)(void), void (*parent)(void),
>                                                void (*child)(void));

After this, the following configure line should work:

CFLAGS="-fomit-frame-pointer -O3 -fpic" CXX=gcc CXXFLAGS="-felide-constructors -fno-exceptions -fno-rtti -O3" ./configure --prefix=/usr/local/mysql --disable-shared

Here is some information that a HPUX Version 11.x user sent us about compiling MySQL with HPUX:x compiler:

 Environment:
      proper compilers.
         setenv CC cc
         setenv CXX aCC
      flags
         setenv CFLAGS -D_REENTRANT
         setenv CXXFLAGS -D_REENTRANT
         setenv CPPFLAGS -D_REENTRANT
     % aCC -V
     aCC: HP ANSI C++ B3910B X.03.14.06
     % cc -V /tmp/empty.c
     cpp.ansi: HP92453-01 A.11.02.00 HP C Preprocessor (ANSI)
     ccom: HP92453-01 A.11.01.00 HP C Compiler
     cc: "/tmp/empty.c", line 1: warning 501: Empty source file.

  configuration:
     ./configure  --with-pthread        \
     --prefix=/source-control/mysql     \
     --with-named-thread-libs=-lpthread \
     --with-low-memory

    added '#define _CTYPE_INCLUDED' to include/m_ctype.h. This
    symbol is the one defined in HP's /usr/include/ctype.h:

     /* Don't include std ctype.h when this is included */
     #define _CTYPE_H
     #define __CTYPE_INCLUDED
     #define _CTYPE_INCLUDED
     #define _CTYPE_USING   /* Don't put names in global namespace. */

I had to use the compile-time flag -D_REENTRANT to get the compiler to recognize the prototype for localtime_r. Alternatively I could have supplied the prototype for localtime_r. But I wanted to catch other bugs without needing to run into them. I wasn't sure where I needed it, so I added it to all flags.
The optimization flags used by MySQL (-O3) are not recognized by HP's compilers. I did not change the flags.

4.12.18 Mac OS X Notes

4.12.18.1 Mac OS X Public beta

MySQL should work without any problems on Mac OS X Public Beta (Darwin). You don't need the pthread patches for this OS!

4.12.18.2 Mac OS X Server

Before trying to configure MySQL on Mac OS X server you must first install the pthread package from http://www.prnet.de/RegEx/mysql.html.

Our binary for Mac OS X is compiled on Rhapsody 5.5 with the following configure line:

CC=gcc CFLAGS="-O2 -fomit-frame-pointer" CXX=gcc CXXFLAGS="-O2 -fomit-frame-pointer" ./configure --prefix=/usr/local/mysql "--with-comment=Official MySQL binary" --with-extra-charsets=complex  --disable-shared

You might want to also add aliases to your shell's resource file to access mysql and mysqladmin from the command line:

alias mysql '/usr/local/mysql/bin/mysql'
alias mysqladmin '/usr/local/mysql/bin/mysqladmin'

4.12.19 BeOS Notes

We are really interested in getting MySQL to work on BeOS, but unfortunately we don't have any person who knows BeOS or has time to do a port.

We are interested in finding someone to do a port, and we will help them with any technical questions they may have while doing the port.

We have previously talked with some BeOS developers that have said that MySQL is 80% ported to BeOS, but we haven't heard from these in a while.

4.13 Windows Notes

This section describes installation and use of MySQL on Windows. This is also described in the `README' file that comes with the MySQL Windows distribution.

4.13.1 Installing MySQL on Windows

If you don't have a copy of the MySQL distribution, you should first download one from http://www.mysql.com/.

If you plan to connect to MySQL from some other program, you will probably also need the MyODBC driver. You can find this at the MyODBC download page (http://www.mysql.com/downloads/api-myodbc.html).

To install either distribution, unzip it in some empty directory and run the Setup.exe program.

By default, MySQL-Windows is configured to be installed in `C:\mysql'. If you want to install MySQL elsewhere, install it in `C:\mysql', then move the installation to where you want it. If you do move MySQL, you must tell mysqld where everything is by supplying options to mysqld. Use C:\mysql\bin\mysqld --help to display all options! For example, if you have moved the MySQL distribution to `D:\programs\mysql', you must start mysqld with: D:\programs\mysql\bin\mysqld --basedir D:\programs\mysql

With all newer MySQL versions, you can also create a `C:\my.cnf' file that holds any default options for the MySQL server. Copy the file `\mysql\my-xxxxx.cnf' to `C:\my.cnf' and edit this to suit your setup. Note that you should specify all paths with `/' instead of `\'. If you use `\', you need to specify this twice, as `\' is the escape character in MySQL. See section 4.16.5 Option Files.

4.13.2 Starting MySQL on Windows 95 or Windows 98

MySQL uses TCP/IP to connect a client to a server. (This will allow any machine on your network to connect to your MySQL server.) Because of this, you must install TCP/IP on your machine before starting MySQL. You can find TCP/IP on your Windows CD-ROM.

Note that if you are using an old Win95 release (for example OSR2), it's likely that you have an old Winsock package! MySQL requires Winsock 2! You can get the newest Winsock from http://www.microsoft.com/. Win98 has the new Winsock 2 library, so the above doesn't apply for Win98.

There are 2 different MySQL servers you can use:

`mysqld`	Compiled with full debugging and automatic memory allocation checking
`mysqld-opt`	Optimized for a Pentium processor.

Both of the above should work on any Intel processor >= i386.

To start the mysqld server, you should start an MS-DOS window and type:

C:\mysql\bin\mysqld

This will start mysqld in the background without a window.

You can kill the MySQL server by executing:

C:\mysql\bin\mysqladmin -u root shutdown

Note that Win95/Win98 don't support creation of named pipes. On Win95/Win98, you can only use named pipes to connect to a remote MySQL running on an NT server.

If mysqld doesn't start, please check whether or not the `\mysql\mysql.err' file contains any reason for this. You can also try to start it with mysqld --standalone; In this case you may get some useful information on the screen that may help solve this.

The last option is to start mysqld with --debug. In this case mysqld will write a log file in `\mysqld.trace' that should contain the reason why mysqld doesn't start. If you make a bug report about this, please only send the lines to the mailing list where something seems to go wrong!

4.13.3 Starting MySQL on NT or Windows 2000

The Win95/Win98 section also applies to MySQL on NT/Win2000, with the following differences:

To get MySQL to work with TCP/IP on NT, you must install service pack 3 (or newer)!

Note that everything in the following that applies for NT also applies for Win2000!

For NT/Win2000, the server name is mysqld-nt. Normally you should install MySQL as a service on NT/Win2000:

C:\mysql\bin\mysqld-nt --install

(You could use the mysqld or mysqld-opt servers on NT, but those cannot be started as a service or use named pipes.)

You can start and stop the MySQL service with:

NET START mysql
NET STOP mysql

Note that in this case you can't use any other options for mysqld-nt!

You can also run mysqld-nt as a stand-alone program on NT if you need to start mysqld-nt with any options! If you start mysqld-nt without options on NT, mysqld-nt tries to starts itself as a service with the default service options. If you have stopped mysqld-nt, you have to start it with NET START mysql.

The service is installed with the name MySQL. Once installed, it must be started using the Services Control Manager (SCM) Utility (found in Control Panel) or by using the NET START MySQL command. If any options are desired, they must be specified as "Startup parameters" in the SCM utility before you start the MySQL service. Once running, mysqld-nt can be stopped using mysqladmin or from the SCM utility or by using the command NET STOP MySQL. If you use SCM to stop mysqld-nt, there is a strange message from SCM about mysqld shutdown normally. When run as a service, mysqld-nt has no access to a console and so no messages can be seen.

On NT you can get the following service error messages:

Permission Denied	Means that it cannot find `mysqld-nt.exe`.
Cannot Register	Means that the path is incorrect.
Failed to install service.	Means that the service is already installed or that the Service Control Manager is in bad state.

If you have problems installing mysqld-nt as a service, try starting it with the full path:

C:\mysql\bin\mysqld-nt --install

If this doesn't work, you can get mysqld-nt to start properly by fixing the path in the registry!

If you don't want to start mysqld-nt as a service, you can start it as follows:

C:\mysql\bin\mysqld-nt --standalone

C:\mysql\bin\mysqld --standalone --debug

The last version gives you a debug trace in `C:\mysqld.trace'.

4.13.4 Running MySQL on Windows

MySQL supports TCP/IP on all Windows platforms and named pipes on NT. The default is to use named pipes for local connections on NT and TCP/IP for all other cases if the client has TCP/IP installed. The host name specifies which protocol is used:

Host name

Protocol
NULL (none)	On NT, try named pipes first; if that doesn't work, use TCP/IP. On Win95/Win98, TCP/IP is used.
.	Named pipes
localhost	TCP/IP to current host
hostname	TCP/IP

You can force a MySQL client to use named pipes by specifying the --pipe option or by specifying . as the host name. Use the --socket option to specify the name of the pipe.

You can test whether or not MySQL is working by executing the following commands:

C:\mysql\bin\mysqlshow
C:\mysql\bin\mysqlshow -u root mysql
C:\mysql\bin\mysqladmin version status proc
C:\mysql\bin\mysql test

If mysqld is slow to answer to connections on Win95/Win98, there is probably a problem with your DNS. In this case, start mysqld with --skip-name-resolve and use only localhost and IP numbers in the MySQL grant tables. You can also avoid DNS when connecting to a mysqld-nt MySQL server running on NT by using the --pipe argument to specify use of named pipes. This works for most MySQL clients.

There are two versions of the MySQL command-line tool:

mysql Compiled on native Windows, which offers very limited text editing capabilities.

mysqlc Compiled with the Cygnus GNU compiler and libraries, which offers readline editing.

If you want to use mysqlc.exe, you must copy `C:\mysql\lib\cygwinb19.dll' to `\windows\system' (or similar place).

The default privileges on Windows give all local users full privileges to all databases. To make MySQL more secure, you should set a password for all users and remove the row in the mysql.user table that has Host='localhost' and User=''.

You should also add a password for the root user. (The following example starts by removing the anonymous user, that allows anyone to access the 'test' database.):

C:\mysql\bin\mysql mysql
mysql> DELETE FROM user WHERE Host='localhost' AND User='';
mysql> QUIT
C:\mysql\bin\mysqladmin reload
C:\mysql\bin\mysqladmin -u root password your_password

After you've set the password, if you want to take down the mysqld server, you can do so using this command:

mysqladmin --user=root --password=your_password shutdown

If you are using the old shareware version of MySQL Version 3.21 under Windows, the above command will fail with an error: parse error near 'SET OPTION password'. This is because the old shareware version, which is based on MySQL Version 3.21, doesn't have the SET PASSWORD command. The fix is in this case to upgrade to the Version 3.22 shareware.

With the newer MySQL versions you can easily add new users and change privileges with GRANT and REVOKE commands. See section 7.35 GRANT and REVOKE Syntax.

4.13.5 Connecting to a Remote MySQL from Windows with SSH

Here is a note about how to connect to get a secure connection to remote MySQL server with SSH (by David Carlson dcarlson@mplcomm.com):

Install an SSH client on your windows machine - As a user, the best non-free one I've found is from SecureCRT from http://www.vandyke.com/. Another option is f-secure from http://www.f-secure.com/. You can also find some free ones on Google at http://directory.google.com/Top/Computers/Security/Products_and_Tools/Cryptography/SSH/Clients/Windows/.
Start your windows SSH client. Set Host_Name = yourmysqlserver_URL_or_IP. Set userid=your_userid to log in to your server (probably not the same as your MySQL login/password.
Set up port forwarding. Either do a remote forward (Set local_port: 3306, remote_host: yourmysqlservername_or_ip, remote_port: 3306 ) or a local forward (Set port: 3306, host: localhost, remote port: 3306).
Save everything, otherwise you'll have to redo it the next time.
Log in to your server with SSH session you just created.
Start some ODBC application on your windows machine (for example Access).
Create a new file in windows and link to MySQL using the ODBC driver the same way you normally do, EXCEPT type in localhost for the MySQL host server - not yourmysqlservername.

You should now have your ODBC connection to MySQL encrypted using SSH.

4.13.6 Splitting Data Across Different Disks Under Windows

On windows MySQL Version 3.23.16 and above is compiled with the -DUSE_SYMDIR option. This allows you to put a database on different disk by adding a symbolic link to it (in a similar manner that symbolic links works on Unix).

On windows you make a symbolic link to a database by creating a file that contains the path to the destination directory and saving this in the `mysql_data' directory under the filename `database.sym'. Note that the symbolic link will only be used if the directory `mysql_data_dir\database' doesn't exist.

For example, if you want to have database foo on `D:\data\foo', you should create the file `C:\mysql\data\foo.sym' that contains the text D:\data\foo. After this, all tables created in the database foo will be created in `D:\data\foo'.

4.13.7 Compiling MySQL Clients on Windows

In your source files, you should include `windows.h' before you include mysql.h:

#if defined(_WIN32) || defined(_WIN64)
#include <windows.h>
#endif
#include <mysql.h>

You can either link your code with the dynamic `libmysql.lib' library, which is just a wrapper to load in `libmysql.dll' on demand, or link with the static `mysqlclient.lib' library.

Note that as the mysqlclient libraries are compiled as threaded libraries, you should also compile your code to be multi-threaded!

4.13.8 Windows and BDB Tables

We will shortly do a full test on the new BDB interface on Windows. When this is done we will start to release binary distributions (for Windows and Unix) of MySQL that will include support for BDB tables.

4.13.9 MySQL-Windows Compared to Unix MySQL

MySQL-Windows has by now proven itself to be very stable. This version of MySQL has the same features as the corresponding Unix version with the following exceptions:

Win95 and threads

Win95 leaks about 200 bytes of main memory for each thread creation. Because of this, you shouldn't run mysqld for an extended time on Win95 if you do many connections, because each connection in MySQL creates a new thread! WinNT and Win98 don't suffer from this bug.

Concurrent reads

MySQL depends on the pread() and pwrite() calls to be able to mix INSERT and SELECT. Currently we use mutexes to emulate pread()/pwrite(). We will, in the long run, replace the file level interface with a virtual interface so that we can use the readfile()/writefile() interface on NT to get more speed. The current implementation will however limit the number of open files MySQL can use to 1024, which means that you will not be able to run as many concurrent threads on NT as on Unix.

Blocking read

MySQL uses a blocking read for each connection. This means that:

A connection will not be disconnected automatically after 8 hours, as happens with the Unix version of MySQL.
If a connection hangs, it's impossible to break it without killing MySQL.
mysqladmin kill will not work on a sleeping connection.
mysqladmin shutdown can't abort as long as there are sleeping connections.

We plan to fix this when our Windows developers have figured out a nice workaround for this.

UDF functions

For the moment, MySQL-Windows does not support user-definable functions.

DROP DATABASE

You can't drop a database that is in use by some thread.

Killing MySQL from the task manager

You can't kill MySQL from the task manager or with the shutdown utility in Win95. You must take it down with mysqladmin shutdown.

Case-insensitive names

Filenames are case insensitive on Windows, so database and table names are also case insensitive in MySQL for Windows. The only restriction is that database and table names must be given in the same case throughout a given statement. See section 7.1.5.1 Case Sensitivity in Names.

The `\' directory character

Pathname components in Win95 are separated by the `\' character, which is also the escape character in MySQL. If you are using

LOAD
DATA INFILE

or SELECT ... INTO OUTFILE, you must double the `\' character or use Unix style filenames `/' characters:

LOAD DATA INFILE "C:\\tmp\\skr.txt" INTO TABLE skr;
SELECT * INTO OUTFILE 'C:/tmp/skr.txt' FROM skr;

Can't open named pipe error

If you use a MySQL 3.22 version on NT with the newest mysql-clients you will get the following error:

error 2017: can't open named pipe to host: . pipe...

This is because the release version of MySQL uses named pipes on NT by default. You can avoid this error by using the --host=localhost option to the new MySQL clients or create a file `C:\my.cnf' that contains the following information:

[client]
host = localhost

Access denied for user error

If you get the error

Access denied for user: 'some-user@unknown'
to database 'mysql'

when accessing a MySQL server on the same machine, this means that MySQL can't resolve your host name properly. To fix this, you should create a file `\windows\hosts' with the following information:

127.0.0.1       localhost

ALTER TABLE

While you are doing an ALTER TABLE the table is locked from usage by other threads. This has to do with the fact that you on Windows can't delete a file that is in use by another threads. (We may in the future find some way to go around this problem.)

DROP TABLE on a table that is in use by a MERGE table will not work.

The MERGE handler does it table mapping hidden from MySQL. Because Windows doesn't allow one to drop files that are open, you have to first flush all MERGE tables (with FLUSH TABLES) or drop the MERGE table before droping the table. We will fix this at the same time we introduce VIEWs.

Here are some open issues for anyone who might want to help us with the Windows release:

Make a single-user MYSQL.DLL server. This should include everything in a standard MySQL server, except thread creation. This will make MySQL much easier to use in applications that don't need a true client/server and don't need to access the server from other hosts.
Add some nice start and shutdown icons to the MySQL installation.
Create a tool to manage registry entries for the MySQL startup options. The registry entry reading is already coded into `mysqld.cc', but it should be recoded to be more parameter oriented. The tool should also be able to update the `\my.cnf' file if the user prefers to use this instead of the registry.
When registering mysqld as a service with --install (on NT) it would be nice if you could also add default options on the command line. For the moment, the workaround is to update the `C:\my.cnf' file instead.
When you suspend a laptop running Win95, the mysqld daemon doesn't accept new connections when the laptop is resumed. We don't know if this is a problem with Win95, TCP/IP, or MySQL.
It would be real nice to be able to kill mysqld from the task manager. For the moment, you must use mysqladmin shutdown.
Port readline to Windows for use in the mysql command line tool.
GUI versions of the standard MySQL clients (mysql, mysqlshow, mysqladmin, and mysqldump) would be nice.
It would be nice if the socket read and write functions in `net.c' were interruptible. This would make it possible to kill open threads with mysqladmin kill on Windows.
Documentation of which Windows programs work with MySQL-Windows or MyODBC and what must be done to get them working.
mysqld always starts in the "C" locale and not in the default locale. We would like to have mysqld use the current locale for the sort order.
Implement UDF functions with .DLLs.
Add macros to use the faster thread-safe increment/decrement methods provided by Windows.

Other Windows-specific issues are described in the `README' file that comes with the MySQL-Windows distribution.

4.14 OS/2 Notes

MySQL uses quite a few open files. Because of this, you should add something like the following to your `CONFIG.SYS' file:

SET EMXOPT=-c -n -h1024

If you don't do this, you will probably run into the following error:

File 'xxxx' not found (Errcode: 24)

When using MySQL with OS/2 Warp 3, FixPack 29 or above is required. With OS/2 Warp 4, FixPack 4 or above is required. This is a requirement of the Pthreads library. MySQL must be installed in a partition that supports long filenames such as HPFS, FAT32, etc.

The `INSTALL.CMD' script must be run from OS/2's own `CMD.EXE' and may not work with replacement shells such as `4OS2.EXE'.

The `scripts/mysql-install-db' script has been renamed. It is now called `install.cmd' and is a REXX script, which will set up the default MySQL security settings and create the WorkPlace Shell icons for MySQL.

Dynamic module support is compiled in but not fully tested. Dynamic modules should be compiled using the Pthreads run-time library.

gcc -Zdll -Zmt -Zcrtdll=pthrdrtl -I../include -I../regex -I.. \
    -o example udf_example.cc -L../lib -lmysqlclient udf_example.def
mv example.dll example.udf

Note: Due to limitations in OS/2, UDF module name stems must not exceed 8 characters. Modules are stored in the `/mysql2/udf' directory; the safe-mysqld.cmd script will put this directory in the BEGINLIBPATH environment variable. When using UDF modules, specified extensions are ignored -- it is assumed to be `.udf'. For example, in Unix, the shared module might be named `example.so' and you would load a function from it like this:

CREATE FUNCTION metaphon RETURNS STRING SONAME "example.so";

Is OS/2, the module would be named `example.udf', but you would not specify the module extension:

CREATE FUNCTION metaphon RETURNS STRING SONAME "example";

4.15 MySQL Binaries

As a service, we at MySQL AB provide a set of binary distributions of MySQL that are compiled at our site or at sites where customers kindly have given us access to their machines.

These distributions are generated with scripts/make_binary_distribution and are configured with the following compilers and options:

SunOS 4.1.4 2 sun4c with gcc 2.7.2.1: CC=gcc CXX=gcc CXXFLAGS="-O3 -felide-constructors" ./configure --prefix=/usr/local/mysql --disable-shared --with-extra-charsets=complex --enable-assembler
SunOS 5.5.1 sun4u with egcs 1.0.3a: CC=gcc CFLAGS="-O3 -fomit-frame-pointer" CXX=gcc CXXFLAGS="-O3 -fomit-frame-pointer -felide-constructors -fno-exceptions -fno-rtti" ./configure --prefix=/usr/local/mysql --with-low-memory --with-extra-charsets=complex
SunOS 5.6 sun4u with egcs 2.90.27: CC=gcc CFLAGS="-O3 -fomit-frame-pointer" CXX=gcc CXXFLAGS="-O3 -fomit-frame-pointer -felide-constructors -fno-exceptions -fno-rtti" ./configure --prefix=/usr/local/mysql --with-low-memory --with-extra-charsets=complex
SunOS 5.6 i86pc with gcc 2.8.1: CC=gcc CXX=gcc CXXFLAGS=-O3 ./configure --prefix=/usr/local/mysql --with-low-memory --with-extra-charsets=complex
Linux 2.0.33 i386 with pgcc 2.90.29 (egcs 1.0.3a): CFLAGS="-O3 -mpentium -mstack-align-double -fomit-frame-pointer" CXX=gcc CXXFLAGS="-O3 -mpentium -mstack-align-double -fomit-frame-pointer -felide-constructors -fno-exceptions -fno-rtti" ./configure --prefix=/usr/local/mysql --enable-assembler --with-mysqld-ldflags=-all-static --with-extra-charsets=complex
Linux 2.2.x with x686 with gcc 2.95.2: CFLAGS="-O3 -mpentiumpro -fomit-frame-pointer" CXX=gcc CXXFLAGS="-O3 -mpentiumpro -fomit-frame-pointer -felide-constructors -fno-exceptions -fno-rtti" ./configure --prefix=/usr/local/mysql --enable-assembler --with-mysqld-ldflags=-all-static --disable-shared --with-extra-charset=complex
SCO 3.2v5.0.4 i386 with gcc 2.7-95q4: CC=gcc CXX=gcc CXXFLAGS=-O3 ./configure --prefix=/usr/local/mysql --with-extra-charsets=complex
AIX 2 4 with gcc 2.7.2.2: CC=gcc CXX=gcc CXXFLAGS=-O3 ./configure --prefix=/usr/local/mysql --with-extra-charsets=complex
OSF1 V4.0 564 alpha with gcc 2.8.1: CC=gcc CFLAGS=-O CXX=gcc CXXFLAGS=-O3 ./configure --prefix=/usr/local/mysql --with-low-memory --with-extra-charsets=complex
Irix 6.3 IP32 with gcc 2.8.0: CC=gcc CXX=gcc CXXFLAGS=-O3 ./configure --prefix=/usr/local/mysql --with-extra-charsets=complex
BSDI BSD/OS 3.1 i386 with gcc 2.7.2.1: CC=gcc CXX=gcc CXXFLAGS=-O ./configure --prefix=/usr/local/mysql --with-extra-charsets=complex
BSDI BSD/OS 2.1 i386 with gcc 2.7.2: CC=gcc CXX=gcc CXXFLAGS=-O3 ./configure --prefix=/usr/local/mysql --with-extra-charsets=complex

Anyone who has more optimal options for any of the configurations listed above can always mail them to the developer's mailing list at internals@lists.mysql.com.

RPM distributions prior to MySQL Version 3.22 are user-contributed. Beginning with Version 3.22, the RPMs are generated by us at MySQL AB.

If you want to compile a debug version of MySQL, you should add --with-debug or --with-debug=full to the above configure lines and remove any -fomit-frame-pointer options.

4.16 Post-installation Setup and Testing

Once you've installed MySQL (from either a binary or source distribution), you need to initialize the grant tables, start the server, and make sure that the server works okay. You may also wish to arrange for the server to be started and stopped automatically when your system starts up and shuts down.

Normally you install the grant tables and start the server like this for installation from a source distribution:

shell> ./scripts/mysql_install_db
shell> cd mysql_installation_directory
shell> ./bin/safe_mysqld --user=mysql &

For a binary distribution, do this:

shell> cd mysql_installation_directory
shell> ./bin/mysql_install_db
shell> ./bin/safe_mysqld --user=mysql &

This creates the mysql database which will hold all database privileges, the test database which you can use to test MySQL and also privilege entries for the user that run mysql_install_db and a root user (without any passwords). This also starts the mysqld server.

mysql_install_db will not overwrite any old privilege tables, so it should be safe to run in any circumstances. If you don't want to have the test database you can remove it with mysqladmin -u root drop test.

Testing is most easily done from the top-level directory of the MySQL distribution. For a binary distribution, this is your installation directory (typically something like `/usr/local/mysql'). For a source distribution, this is the main directory of your MySQL source tree.

In the commands shown below in this section and in the following subsections, BINDIR is the path to the location in which programs like mysqladmin and safe_mysqld are installed. For a binary distribution, this is the `bin' directory within the distribution. For a source distribution, BINDIR is probably `/usr/local/bin', unless you specified an installation directory other than `/usr/local' when you ran configure. EXECDIR is the location in which the mysqld server is installed. For a binary distribution, this is the same as BINDIR. For a source distribution, EXECDIR is probably `/usr/local/libexec'.

Testing is described in detail below:

If necessary, start the mysqld server and set up the initial MySQL grant tables containing the privileges that determine how users are allowed to connect to the server. This is normally done with the mysql_install_db script:
```
shell> scripts/mysql_install_db
```
Typically, mysql_install_db needs to be run only the first time you install MySQL. Therefore, if you are upgrading an existing installation, you can skip this step. (However, mysql_install_db is quite safe to use and will not update any tables that already exist, so if you are unsure of what to do, you can always run mysql_install_db.) mysql_install_db creates six tables (user, db, host, tables_priv, columns_priv, and func) in the mysql database. A description of the initial privileges is given in section 6.13 Setting Up the Initial MySQL Privileges. Briefly, these privileges allow the MySQL root user to do anything, and allow anybody to create or use databases with a name of 'test' or starting with 'test_'. If you don't set up the grant tables, the following error will appear in the log file when you start the server:
```
mysqld: Can't find file: 'host.frm'
```
The above may also happen with a binary MySQL distribution if you don't start MySQL by executing exactly ./bin/safe_mysqld! See section 15.3 safe_mysqld, the wrapper around mysqld. You might need to run mysql_install_db as root. However, if you prefer, you can run the MySQL server as an unprivileged (non-root) user, provided that user can read and write files in the database directory. Instructions for running MySQL as an unprivileged user are given in section 21.9 How to Run MySQL As a Normal User. If you have problems with mysql_install_db, see section 4.16.1 Problems Running mysql_install_db. There are some alternatives to running the mysql_install_db script as it is provided in the MySQL distribution:
- You may want to edit mysql_install_db before running it, to change the initial privileges that are installed into the grant tables. This is useful if you want to install MySQL on a lot of machines with the same privileges. In this case you probably should need only to add a few extra INSERT statements to the mysql.user and mysql.db tables!
- If you want to change things in the grant tables after installing them, you can run mysql_install_db, then use mysql -u root mysql to connect to the grant tables as the MySQL root user and issue SQL statements to modify the grant tables directly.
- It is possible to re-create the grant tables completely after they have already been created. You might want to do this if you've already installed the tables but then want to re-create them after editing mysql_install_db.
For more information about these alternatives, see section 6.13 Setting Up the Initial MySQL Privileges.
Start the MySQL server like this:
```
shell> cd mysql_installation_directory
shell> bin/safe_mysqld &
```
If you have problems starting the server, see section 4.16.2 Problems Starting the MySQL Server.

Use mysqladmin to verify that the server is running. The following commands provide a simple test to check that the server is up and responding to connections:

shell> BINDIR/mysqladmin version
shell> BINDIR/mysqladmin variables

The output from mysqladmin version varies slightly depending on your platform and version of MySQL, but should be similar to that shown below:

shell> BINDIR/mysqladmin version
mysqladmin  Ver 8.14 Distrib 3.23.32, for linux on i586
Copyright (C) 2000 MySQL AB & MySQL Finland AB & TCX DataKonsult AB
This software comes with ABSOLUTELY NO WARRANTY. This is free software,
and you are welcome to modify and redistribute it under the GPL license

Server version          3.23.32-debug
Protocol version        10
Connection              Localhost via Unix socket
TCP port                3306
UNIX socket             /tmp/mysql.sock
Uptime:                 16 sec

Threads: 1  Questions: 9  Slow queries: 0  Opens: 7  Flush tables: 2  Open tables: 0 Queries per second avg: 0.000  Memory in use: 132K  Max memory used: 16773K

To get a feeling for what else you can do with BINDIR/mysqladmin, invoke it with the --help option.

Verify that you can shut down the server:

shell> BINDIR/mysqladmin -u root shutdown

Verify that you can restart the server. Do this using safe_mysqld or by invoking mysqld directly. For example:
```
shell> BINDIR/safe_mysqld --log &
```
If safe_mysqld fails, try running it from the MySQL installation directory (if you are not already there). If that doesn't work, see section 4.16.2 Problems Starting the MySQL Server.
Run some simple tests to verify that the server is working. The output should be similar to what is shown below:
```
shell> BINDIR/mysqlshow
+-----------+
| Databases |
+-----------+
| mysql     |
+-----------+

shell> BINDIR/mysqlshow mysql
Database: mysql
+--------------+
|    Tables    |
+--------------+
| columns_priv |
| db           |
| func         |
| host         |
| tables_priv  |
| user         |
+--------------+

shell> BINDIR/mysql -e "select host,db,user from db" mysql
+------+--------+------+
| host | db     | user |
+------+--------+------+
| %    | test   |      |
| %    | test_% |      |
+------+--------+------+
```
There is also a benchmark suite in the `sql-bench' directory (under the MySQL installation directory) that you can use to compare how MySQL performs on different platforms. The `sql-bench/Results' directory contains the results from many runs against different databases and platforms. To run all tests, execute these commands:
```
shell> cd sql-bench
shell> run-all-tests
```
If you don't have the `sql-bench' directory, you are probably using an RPM for a binary distribution. (Source distribution RPMs include the benchmark directory.) In this case, you must first install the benchmark suite before you can use it. Beginning with MySQL Version 3.22, there are benchmark RPM files named `mysql-bench-VERSION-i386.rpm' that contain benchmark code and data. If you have a source distribution, you can also run the tests in the `tests' subdirectory. For example, to run `auto_increment.tst', do this:
```
shell> BINDIR/mysql -vvf test < ./tests/auto_increment.tst
```
The expected results are shown in the `./tests/auto_increment.res' file.

4.16.1 Problems Running `mysql_install_db`

The purpose of the mysql_install_db script is to generate new MySQL privilege tables. It will not affect any other data! It will also not do anything if you already have MySQL privilege tables installed!

If you want to re-create your privilege tables, you should take down the mysqld server, if it's running, and then do something like:

mv mysql-data-directory/mysql mysql-data-directory/mysql-old
mysql_install_db

This section lists problems you might encounter when you run mysql_install_db:

mysql_install_db doesn't install the grant tables

You may find that mysql_install_db fails to install the grant tables and terminates after displaying the following messages:

starting mysqld daemon with databases from XXXXXX
mysql daemon ended

In this case, you should examine the log file very carefully! The log should be located in the directory `XXXXXX' named by the error message, and should indicate why mysqld didn't start. If you don't understand what happened, include the log when you post a bug report using mysqlbug! See section 2.3 How to Report Bugs or Problems.

There is already a mysqld daemon running

In this case, you probably don't have to run mysql_install_db at all. You have to run mysql_install_db only once, when you install MySQL the first time.

Installing a second mysqld daemon doesn't work when one daemon is running

This can happen when you already have an existing MySQL installation, but want to put a new installation in a different place (for example, for testing, or perhaps you simply want to run two installations at the same time). Generally the problem that occurs when you try to run the second server is that it tries to use the same socket and port as the old one. In this case you will get the error message:

Can't start server: Bind on
TCP/IP port: Address already in use

Can't start server : Bind on
unix socket...

. See section 4.17 Installing Many Servers on the Same Machine.

You don't have write access to `/tmp'

If you don't have write access to create a socket file at the default place (in `/tmp') or permission to create temporary files in `/tmp,' you will get an error when running mysql_install_db or when starting or using mysqld. You can specify a different socket and temporary directory as follows:

shell> TMPDIR=/some_tmp_dir/
shell> MYSQL_UNIX_PORT=/some_tmp_dir/mysqld.sock
shell> export TMPDIR MYSQL_UNIX_PORT

`some_tmp_dir' should be the path to some directory for which you have write permission. See section A Environment Variables. After this you should be able to run mysql_install_db and start the server with these commands:

shell> scripts/mysql_install_db
shell> BINDIR/safe_mysqld &

mysqld crashes immediately

If you are running RedHat Version 5.0 with a version of glibc older than 2.0.7-5, you should make sure you have installed all glibc patches! There is a lot of information about this in the MySQL mail archives. Links to the mail archives are available online at http://www.mysql.com/documentation/. Also, see section 4.12.5 Linux Notes (All Linux Versions). You can also start mysqld manually using the --skip-grant-tables option and add the privilege information yourself using mysql:

shell> BINDIR/safe_mysqld --skip-grant-tables &
shell> BINDIR/mysql -u root mysql

From mysql, manually execute the SQL commands in mysql_install_db. Make sure you run

mysqladmin
flush-privileges

or mysqladmin reload afterward to tell the server to reload the grant tables.

4.16.2 Problems Starting the MySQL Server

Generally, you start the mysqld server in one of three ways:

By invoking mysql.server. This script is used primarily at system startup and shutdown, and is described more fully in section 4.16.3 Starting and Stopping MySQL Automatically.
By invoking safe_mysqld, which tries to determine the proper options for mysqld and then runs it with those options. See section 15.3 safe_mysqld, the wrapper around mysqld.
On NT you should install mysqld as a service as follows:
```
bin\mysqld-nt --install               # Install MySQL as a service
```
You can now start/stop mysqld as follows:
```
NET START mysql
NET STOP mysql
```
Note that in this case you can't use any other options for mysqld! You can remove the service as follows:
```
bin\mysqld-nt --remove                # remove MySQL as a service
```
By invoking mysqld directly.

When the mysqld daemon starts up, it changes directory to the data directory. This is where it expects to write log files and the pid (process ID) file, and where it expects to find databases.

The data directory location is hardwired in when the distribution is compiled. However, if mysqld expects to find the data directory somewhere other than where it really is on your system, it will not work properly. If you have problems with incorrect paths, you can find out what options mysqld allows and what the default path settings are by invoking mysqld with the --help option. You can override the defaults by specifying the correct pathnames as command-line arguments to mysqld. (These options can be used with safe_mysqld as well.)

Normally you should need to tell mysqld only the base directory under which MySQL is installed. You can do this with the --basedir option. You can also use --help to check the effect of changing path options (note that --help must be the final option of the mysqld command). For example:

shell> EXECDIR/mysqld --basedir=/usr/local --help

Once you determine the path settings you want, start the server without the --help option.

Whichever method you use to start the server, if it fails to start up correctly, check the log file to see if you can find out why. Log files are located in the data directory (typically `/usr/local/mysql/data' for a binary distribution, `/usr/local/var' for a source distribution, `\mysql\mysql.err' on Windows.) Look in the data directory for files with names of the form `host_name.err' and `host_name.log' where host_name is the name of your server host. Then check the last few lines of these files:

shell> tail host_name.err
shell> tail host_name.log

If you find something like the following in the log file:

000729 14:50:10  bdb:  Recovery function for LSN 1 27595 failed
000729 14:50:10  bdb:  warning: ./test/t1.db: No such file or directory
000729 14:50:10  Can't init databases

This means that you didn't start mysqld with --bdb-no-recover and Berkeley DB found something wrong with its log files when it tried to recover your databases. To be able to continue, you should move away the old Berkeley DB log file from the database directory to some other place, where you can later examine these. The log files are named `log.0000000001', where the number will increase over time.

If you are running mysqld with BDB table support and mysqld core dumps at start this could be because of some problems with the BDB recover log. In this case you can try starting mysqld with --bdb-no-recover. If this helps, then you should remove all `log.*' files from the data directory and try starting mysqld again.

If you get the following error, it means that some other program (or another mysqld server) is already using the TCP/IP port or socket mysqld is trying to use:

Can't start server: Bind on TCP/IP port: Address already in use
  or
Can't start server : Bind on unix socket...

Use ps to make sure that you don't have another mysqld server running. If you can't find another server running, you can try to execute the command telnet your-host-name tcp-ip-port-number and press RETURN a couple of times. If you don't get an error message like telnet: Unable to connect to remote host: Connection refused, something is using the TCP/IP port mysqld is trying to use. See section 4.16.1 Problems Running mysql_install_db and section 22.3 Running Multiple MySQL Servers on the Same Machine.

If mysqld is currently running, you can find out what path settings it is using by executing this command:

shell> mysqladmin variables

or

shell> mysqladmin -h 'your-host-name' variables

If safe_mysqld starts the server but you can't connect to it, you should make sure you have an entry in `/etc/hosts' that looks like this:

127.0.0.1       localhost

This problem occurs only on systems that don't have a working thread library and for which MySQL must be configured to use MIT-pthreads.

On Windows, you can try to start mysqld as follows:

C:\mysql\bin\mysqld --standalone --debug

This will not run in the background and it should also write a trace in `\mysqld.trace', which may help you determine the source of your problems. See section 4.13 Windows Notes.

If you are using BDB (Berkeley DB) tables, you should familiarize yourself with the different BDB specific startup options. See section 8.5.3 BDB startup options.

If you are using Gemini tables, refer to the Gemini-specific startup options. See section 8.6.2 GEMINI startup options.

If you are using Innodb tables, refer to the Innodb-specific startup options. See section 8.7.2 InnoDB startup options.

4.16.3 Starting and Stopping MySQL Automatically

The mysql.server script can be used to start or stop the server by invoking it with start or stop arguments:

shell> mysql.server start
shell> mysql.server stop

mysql.server can be found in the `share/mysql' directory under the MySQL installation directory or in the `support-files' directory of the MySQL source tree.

Before mysql.server starts the server, it changes directory to the MySQL installation directory, then invokes safe_mysqld. You might need to edit mysql.server if you have a binary distribution that you've installed in a non-standard location. Modify it to cd into the proper directory before it runs safe_mysqld. If you want the server to run as some specific user, you can change the mysql_daemon_user=root line to use another user. You can also modify mysql.server to pass other options to safe_mysqld.

mysql.server stop brings down the server by sending a signal to it. You can take down the server manually by executing mysqladmin shutdown.

You might want to add these start and stop commands to the appropriate places in your `/etc/rc*' files when you start using MySQL for production applications. Note that if you modify mysql.server, then upgrade MySQL sometime, your modified version will be overwritten, so you should make a copy of your edited version that you can reinstall.

If your system uses `/etc/rc.local' to start external scripts, you should append the following to it:

/bin/sh -c 'cd /usr/local/mysql ; ./bin/safe_mysqld --user=mysql &'

You can also add options for mysql.server in a global `/etc/my.cnf' file. A typical `/etc/my.cnf' file might look like this:

[mysqld]
datadir=/usr/local/mysql/var
socket=/tmp/mysqld.sock
port=3306

[mysql.server]
user=mysql
basedir=/usr/local/mysql

The mysql.server script uses the following variables: user, datadir, basedir, bindir, and pid-file.

The following table shows which option sections each of the startup script uses:

`mysqld`	`mysqld` and `server`
`mysql.server`	`mysql.server`, `mysqld` and `server`
`safe_mysqld`	`mysql.server`, `mysqld` and `server`

See section 4.16.5 Option Files.

4.16.4 mysqld Command-line Options

mysqld accepts the following command-line options:

--ansi

Use ANSI SQL syntax instead of MySQL syntax. See section 5.2 Running MySQL in ANSI Mode.

-b, --basedir=path

Path to installation directory. All paths are usually resolved relative to this.

--big-tables

Allow big result sets by saving all temporary sets on file. It solves most 'table full' errors, but also slows down the queries where in-memory tables would suffice. Since Version 3.23.2, MySQL is able to solve it automatically by using memory for small temporary tables and switching to disk tables where necessary.

--bind-address=IP

IP address to bind to.

--character-sets-dir=path

Directory where character sets are. See section 10.1.1 The Character Set Used for Data and Sorting.

--chroot=path

Chroot mysqld daemon during startup. Recommended security measure. It will somewhat limit LOAD DATA INFILE and SELECT ... INTO OUTFILE though.

-h, --datadir=path

Path to the database root.

--default-character-set=charset

Set the default character set. See section 10.1.1 The Character Set Used for Data and Sorting.

--default-table-type=type

Set the default table type for tables. See section 8 MySQL Table Types.

--debug[...]=

If MySQL is configured with --with-debug, you can use this option to get a trace file of what mysqld is doing. See section I.3 The DBUG package..

--delay-key-write-for-all-tables

Don't flush key buffers between writes for any MyISAM table. See section 13.2.3 Tuning Server Parameters.

--enable-locking

Enable system locking. Note that if you use this option on a system which a not fully working lockd() (as on Linux) you will easily get mysqld to deadlock.

-T, --exit-info

This is a bit mask of different flags one can use for debugging the mysqld server; One should not use this option if one doesn't know exactly what it does!

--flush

Flush all changes to disk after each SQL command. Normally MySQL only does a write of all changes to disk after each SQL command and lets the operating system handle the syncing to disk. See section 21.2 What to Do if MySQL Keeps Crashing.

-?, --help

Display short help and exit.

--init-file=file

Read SQL commands from this file at startup.

-L, --language=...

Client error messages in given language. May be given as a full path. See section 10.1 What Languages Are Supported by MySQL?.

-l, --log[=file]

Log connections and queries to file. See section 23.2 The Query Log.

--log-isam[=file]

Log all ISAM/MyISAM changes to file (only used when debugging ISAM/MyISAM).

--log-slow-queries[=file]

Log all queries that have taken more than long_query_time seconds to execute to file. See section 23.5 The Slow Query Log.

--log-update[=file]

Log updates to file.# where # is a unique number if not given. See section 23.3 The Update Log.

--log-long-format

Log some extra information to update log. If you are using --log-slow-queries then queries that are not using indexes are logged to the slow query log.

--low-priority-updates

Table-modifying operations (INSERT/DELETE/UPDATE) will have lower priority than selects. It can also be done via {INSERT | REPLACE | UPDATE | DELETE} LOW_PRIORITY ... to lower the priority of only one query, or by SET OPTION SQL_LOW_PRIORITY_UPDATES=1 to change the priority in one thread. See section 13.2.9 Table Locking Issues.

--memlock

Lock the mysqld process in memory. This works only if your system supports the mlockall() system call. This may help if you have a problem where the operating system is causing mysqld to swap on disk.

--myisam-recover [=option[,option...]]] where option is one of DEFAULT, BACKUP, FORCE or QUICK.

If this option is used, mysqld will on open check if the table is marked as crashed or if if the table wasn't closed properly. (The last option only works if you are running with --skip-locking). If this is the case mysqld will run check on the table. If the table was corrupted, mysqld will attempt to repair it. The following options affects how the repair works.

DEFAULT	The same as not giving any option to `--myisam-recover`.
BACKUP	If the data table was changed during recover, save a backup of the `table_name.MYD' data file as `table_name-datetime.BAK'.
FORCE	Run recover even if we will loose more than one row from the .MYD file.
QUICK	Don't check the rows in the table if there isn't any delete blocks.

Before a table is automatically repaired, MySQL will add a note about this in the error log. If you want to be able to recover from most things without user intervention, you should use the options BACKUP,FORCE. This will force a repair of a table even if some rows would be deleted, but it will keep the old data file as a backup so that you can later examine what happened.

--pid-file=path

Path to pid file used by safe_mysqld.

-P, --port=...

Port number to listen for TCP/IP connections.

-o, --old-protocol

Use the 3.20 protocol for compatibility with some very old clients. See section 4.18.3 Upgrading from Version 3.20 to Version 3.21.

--one-thread

Only use one thread (for debugging under Linux). See section I.1 Debugging a MySQL server.

-O, --set-variable var=option

Give a variable a value. --help lists variables. You can find a full description for all variables in the SHOW VARIABLES section in this manual. See section 7.28.4 SHOW VARIABLES. The tuning server parameters section includes information of how to optimize these. See section 13.2.3 Tuning Server Parameters.

--safe-mode

Skip some optimize stages. Implies --skip-delay-key-write.

--safe-show-database

Don't show databases for which the user doesn't have any privileges.

--secure

IP numbers returned by the gethostbyname() system call are checked to make sure they resolve back to the original hostname. This makes it harder for someone on the outside to get access by pretending to be another host. This option also adds some sanity checks of hostnames. The option is turned off by default in MySQL Version 3.21 because sometimes it takes a long time to perform backward resolutions. MySQL Version 3.22 caches hostnames (unless --skip-host-cache is used) and has this option enabled by default.

--skip-concurrent-insert

Turn off the ability to select and insert at the same time on MyISAM tables. (This is only to be used if you think you have found a bug in this feature).

--skip-delay-key-write

Ignore the delay_key_write option for all tables. See section 13.2.3 Tuning Server Parameters.

-Sg, --skip-grant-tables

This option causes the server not to use the privilege system at all. This gives everyone full access to all databases! (You can tell a running server to start using the grant tables again by executing

mysqladmin
flush-privileges

or mysqladmin reload.)

--skip-locking

Don't use system locking. To use isamchk or myisamchk you must shut down the server. See section 1.7 How Stable Is MySQL?. Note that in MySQL Version 3.23 you can use REPAIR and CHECK to repair/check MyISAM tables.

--skip-name-resolve

Hostnames are not resolved. All Host column values in the grant tables must be IP numbers or localhost. See section 13.2.10 How MySQL uses DNS.

--skip-networking

Don't listen for TCP/IP connections at all. All interaction with mysqld must be made via Unix sockets. This option is highly recommended for systems where only local requests are allowed. See section 13.2.10 How MySQL uses DNS.

--skip-host-cache

Never use host name cache for faster name-ip resolution, but query DNS server on every connect instead. See section 13.2.10 How MySQL uses DNS.

--skip-new

Don't use new, possible wrong routines. Implies --skip-delay-key-write. This will also set default table type to ISAM. See section 8.3 ISAM Tables.

--skip-safemalloc

If MySQL is configured with --with-debug=full, all programs will check the memory for overruns for every memory allocation and memory freeing. As this checking is very slow, you can avoid this, when you don't need memory checking, by using this option.

--skip-show-database

Don't allow 'SHOW DATABASE' commands, unless the user has process privilege.

--skip-thread-priority

Disable using thread priorities for faster response time.

--socket=path

Socket file to use for local connections instead of default /tmp/mysql.sock.

transaction-isolation= { READ-UNCOMMITTED | READ-COMMITTED | REPEATABLE-READ | SERIALIZABLE }

Sets the default transaction isolation level. See section 7.34 SET TRANSACTION Syntax.

-t, --tmpdir=path

Path for temporary files. It may be useful if your default /tmp directory resides on a partition too small to hold temporary tables.

-u, --user=user_name

Run mysqld daemon as user user_name. This option is mandatory when starting mysqld as root.

-V, --version

Output version information and exit.

4.16.5 Option Files

MySQL can, since Version 3.22, read default startup options for the server and for clients from option files.

MySQL reads default options from the following files on Unix:

Filename Purpose

/etc/my.cnf Global options

DATADIR/my.cnf Server-specific options

defaults-extra-file The file specified with --defaults-extra-file=#

~/.my.cnf User-specific options

DATADIR is the MySQL data directory (typically `/usr/local/mysql/data' for a binary installation or `/usr/local/var' for a source installation). Note that this is the directory that was specified at configuration time, not the one specified with --datadir when mysqld starts up! (--datadir has no effect on where the server looks for option files, because it looks for them before it processes any command-line arguments.)

MySQL reads default options from the following files on Windows:

Filename	Purpose
`windows-system-directory\my.ini`	Global options
`C:\my.cnf`	Global options
`C:\mysql\data\my.cnf`	Server-specific options

Note that on Windows, you should specify all paths with / instead of \. If you use \, you need to specify this twice, as \ is the escape character in MySQL.

MySQL tries to read option files in the order listed above. If multiple option files exist, an option specified in a file read later takes precedence over the same option specified in a file read earlier. Options specified on the command line take precedence over options specified in any option file. Some options can be specified using environment variables. Options specified on the command line or in option files take precedence over environment variable values. See section A Environment Variables.

The following programs support option files: mysql, mysqladmin, mysqld, mysqldump, mysqlimport, mysql.server, myisamchk, and myisampack.

You can use option files to specify any long option that a program supports! Run the program with --help to get a list of available options.

An option file can contain lines of the following forms:

#comment: Comment lines start with `#' or `;'. Empty lines are ignored.
[group]: group is the name of the program or group for which you want to set options. After a group line, any option or set-variable lines apply to the named group until the end of the option file or another group line is given.
option: This is equivalent to --option on the command line.
option=value: This is equivalent to --option=value on the command line.
set-variable = variable=value: This is equivalent to --set-variable variable=value on the command line. This syntax must be used to set a mysqld variable.

The client group allows you to specify options that apply to all MySQL clients (not mysqld). This is the perfect group to use to specify the password you use to connect to the server. (But make sure the option file is readable and writable only by yourself.)

Note that for options and values, all leading and trailing blanks are automatically deleted. You may use the escape sequences `\b', `\t', `\n', `\r', `\\', and `\s' in your value string (`\s' == blank).

Here is a typical global option file:

[client]
port=3306
socket=/tmp/mysql.sock

[mysqld]
port=3306
socket=/tmp/mysql.sock
set-variable = key_buffer_size=16M
set-variable = max_allowed_packet=1M

[mysqldump]
quick

Here is typical user option file:

[client]
# The following password will be sent to all standard MySQL clients
password=my_password

[mysql]
no-auto-rehash
set-variable = connect_timeout=2

[mysql-hot-copy]
interactive-timeout

If you have a source distribution, you will find sample configuration files named `my-xxxx.cnf' in the `support-files' directory. If you have a binary distribution, look in the `DIR/share/mysql' directory, where DIR is the pathname to the MySQL installation directory (typically `/usr/local/mysql'). Currently there are sample configuration files for small, medium, large, and very large systems. You can copy `my-xxxx.cnf' to your home directory (rename the copy to `.my.cnf') to experiment with this.

All MySQL clients that support option files support the following options:

--no-defaults	Don't read any option files.
--print-defaults	Print the program name and all options that it will get.
--defaults-file=full-path-to-default-file	Only use the given configuration file.
--defaults-extra-file=full-path-to-default-file	Read this configuration file after the global configuration file but before the user configuration file.

Note that the above options must be first on the command line to work! --print-defaults may however be used directly after the --defaults-xxx-file commands.

Note for developers: Option file handling is implemented simply by processing all matching options (that is, options in the appropriate group) before any command-line arguments. This works nicely for programs that use the last instance of an option that is specified multiple times. If you have an old program that handles multiply-specified options this way but doesn't read option files, you need add only two lines to give it that capability. Check the source code of any of the standard MySQL clients to see how to do this.

In shell scripts you can use the `my_print_defaults' command to parse the config files:


shell> my_print_defaults client mysql
--port=3306
--socket=/tmp/mysql.sock
--no-auto-rehash

The above output contains all options for the groups 'client' and 'mysql'.

4.17 Installing Many Servers on the Same Machine

In some cases you may want to have many different mysqld daemons (servers) running on the same machine. You may for example want to run a new version of MySQL for testing together with an old version that is in production. Another case is when you want to give different users access to different mysqld servers that they manage themselves.

One way to get a new server running is by starting it with a different socket and port as follows:

shell> MYSQL_UNIX_PORT=/tmp/mysqld-new.sock
shell> MYSQL_TCP_PORT=3307
shell> export MYSQL_UNIX_PORT MYSQL_TCP_PORT
shell> scripts/mysql_install_db
shell> bin/safe_mysqld &

The environment variables appendix includes a list of other environment variables you can use to affect mysqld. See section A Environment Variables.

The above is the quick and dirty way that one commonly uses for testing. The nice thing with this is that all connections you do in the above shell will automatically be directed to the new running server!

If you need to do this more permanently, you should create an own option file for each server. See section 4.16.5 Option Files. In your startup script that is executed at boot time (mysql.server?) you should specify for both servers:

safe_mysqld --default-file=path-to-option-file

At least the following options should be different per server:

port=#
socket=path
pid-file=path

The following options should be different, if they are used:

log=path
log-bin=path
log-update=path
log-isam=path
bdb-logdir=path

If you want more performance, you can also specify the following differently:

tmpdir=path
bdb-tmpdir=path

See section 4.16.4 mysqld Command-line Options.

If you are installing binary MySQL versions (.tar files) and start them with ./bin/safe_mysqld then in most cases the only option you need to add/change is the socket and port argument to safe_mysqld.

4.18 Upgrading/Downgrading MySQL

You can always move the MySQL form and data files between different versions on the same architecture as long as you have the same base version of MySQL. The current base version is 3. If you change the character set when running MySQL (which may also change the sort order), you must run myisamchk -r -q on all tables. Otherwise your indexes may not be ordered correctly.

If you are afraid of new versions, you can always rename your old mysqld to something like mysqld-'old-version-number'. If your new mysqld then does something unexpected, you can simply shut it down and restart with your old mysqld!

When you do an upgrade you should also back up your old databases, of course.

If after an upgrade, you experience problems with recompiled client programs, like Commands out of sync or unexpected core dumps, you probably have used an old header or library file when compiling your programs. In this case you should check the date for your `mysql.h' file and `libmysqlclient.a' library to verify that they are from the new MySQL distribution. If not, please recompile your programs!

If you get some problems that the new mysqld server doesn't want to start or that you can't connect without a password, check that you don't have some old `my.cnf' file from your old installation! You can check this with: program-name --print-defaults. If this outputs anything other than the program name, you have an active my.cnf file that will affect things!

4.18.1 Upgrading From Version 3.22 to Version 3.23

MySQL Version 3.23 supports tables of the new MyISAM type and the old ISAM type. You don't have to convert your old tables to use these with Version 3.23. By default, all new tables will be created with type MyISAM (unless you start mysqld with the --default-table-type=isam option). You can change an ISAM table to a MyISAM table with ALTER TABLE or the Perl script mysql_convert_table_format.

Version 3.22 and 3.21 clients will work without any problems with a Version 3.23 server.

The following lists tell what you have to watch out for when upgrading to Version 3.23:

All tables that uses the tis620 character set must be fixed with myisamchk -r or REPAIR TABLE.
If you do a DROP DATABASE on a symbolic linked database, both the link and the original database is deleted. (This didn't happen in 3.22 because configure didn't detect the readlink system call).
OPTIMIZE TABLE now only works for MyISAM tables. For other table types, you can use ALTER TABLE to optimize the table. During OPTIMIZE TABLE the table is now locked from other threads.
The MySQL client mysql is now by default started with the option --no-named-commands (-g). This option can be disabled with --enable-named-commands (-G). This may cause incompatibility problems in some cases, for example in SQL scripts that use named commands without a semicolon! Long format commands still work from the first line.
If you are using the german character sort order, you must repair all your tables with isamchk -r, as we have made some changes in the sort order!
The default return type of IF will now depend on both arguments and not only the first argument.
AUTO_INCREMENT will not work with negative numbers. The reason for this is that negative numbers caused problems when wrapping from -1 to 0. AUTO_INCREMENT is now for MyISAM tables handled at a lower level and is much faster than before. For MyISAM tables old numbers are also not reused anymore, even if you delete some rows from the table.
CASE, DELAYED, ELSE, END, FULLTEXT, INNER, RIGHT, THEN and WHEN are now reserved words.
FLOAT(X) is now a true floating-point type and not a value with a fixed number of decimals.
When declaring DECIMAL(length,dec) the length argument no longer includes a place for the sign or the decimal point.
A TIME string must now be of one of the following formats: [[[DAYS] [H]H:]MM:]SS[.fraction] or [[[[[H]H]H]H]MM]SS[.fraction]
LIKE now compares strings using the same character comparison rules as '='. If you require the old behavior, you can compile MySQL with the CXXFLAGS=-DLIKE_CMP_TOUPPER flag.
REGEXP is now case insensitive for normal (not binary) strings.
When you check/repair tables you should use CHECK TABLE or myisamchk for MyISAM tables (.MYI) and isamchk for ISAM (.ISM) tables.
If you want your mysqldump files to be compatible between MySQL Version 3.22 and Version 3.23, you should not use the --opt or --full option to mysqldump.
Check all your calls to DATE_FORMAT() to make sure there is a `%' before each format character. (Later MySQL Version 3.22 did allow this syntax.)
mysql_fetch_fields_direct is now a function (it was a macro) and it returns a pointer to a MYSQL_FIELD instead of a MYSQL_FIELD.
mysql_num_fields() can no longer be used on a MYSQL* object (it's now a function that takes MYSQL_RES* as an argument. You should now use mysql_field_count() instead.
In MySQL Version 3.22, the output of SELECT DISTINCT ... was almost always sorted. In Version 3.23, you must use GROUP BY or ORDER BY to obtain sorted output.
SUM() now returns NULL, instead of 0, if there is no matching rows. This is according to ANSI SQL.
An AND or OR with NULL values will now return NULL instead of 0. This mostly affects queries that use NOT on an AND/OR expression as NOT NULL = NULL. LPAD() and RPAD() will shorten the result string if it's longer than the length argument.

4.18.2 Upgrading from Version 3.21 to Version 3.22

Nothing that affects compatibility has changed between Version 3.21 and 3.22. The only pitfall is that new tables that are created with DATE type columns will use the new way to store the date. You can't access these new fields from an old version of mysqld.

After installing MySQL Version 3.22, you should start the new server and then run the mysql_fix_privilege_tables script. This will add the new privileges that you need to use the GRANT command. If you forget this, you will get Access denied when you try to use ALTER TABLE, CREATE INDEX, or DROP INDEX. If your MySQL root user requires a password, you should give this as an argument to mysql_fix_privilege_tables.

The C API interface to mysql_real_connect() has changed. If you have an old client program that calls this function, you must place a 0 for the new db argument (or recode the client to send the db element for faster connections). You must also call mysql_init() before calling mysql_real_connect()! This change was done to allow the new mysql_options() function to save options in the MYSQL handler structure.

The mysqld variable key_buffer has changed names to key_buffer_size, but you can still use the old name in your startup files.

4.18.3 Upgrading from Version 3.20 to Version 3.21

If you are running a version older than Version 3.20.28 and want to switch to Version 3.21, you need to do the following:

You can start the mysqld Version 3.21 server with safe_mysqld --old-protocol to use it with clients from a Version 3.20 distribution. In this case, the new client function mysql_errno() will not return any server error, only CR_UNKNOWN_ERROR (but it works for client errors), and the server uses the old password() checking rather than the new one.

If you are NOT using the --old-protocol option to mysqld, you will need to make the following changes:

All client code must be recompiled. If you are using ODBC, you must get the new MyODBC 2.x driver.
The script scripts/add_long_password must be run to convert the Password field in the mysql.user table to CHAR(16).
All passwords must be reassigned in the mysql.user table (to get 62-bit rather than 31-bit passwords).
The table format hasn't changed, so you don't have to convert any tables.

MySQL Version 3.20.28 and above can handle the new user table format without affecting clients. If you have a MySQL version earlier than Version 3.20.28, passwords will no longer work with it if you convert the user table. So to be safe, you should first upgrade to at least Version 3.20.28 and then upgrade to Version 3.21.

The new client code works with a 3.20.x mysqld server, so if you experience problems with 3.21.x, you can use the old 3.20.x server without having to recompile the clients again.

If you are not using the --old-protocol option to mysqld, old clients will issue the error message:

ERROR: Protocol mismatch. Server Version = 10 Client Version = 9

The new Perl DBI/DBD interface also supports the old mysqlperl interface. The only change you have to make if you use mysqlperl is to change the arguments to the connect() function. The new arguments are: host, database, user, password (the user and password arguments have changed places). See section 24.2.2 The DBI Interface.

The following changes may affect queries in old applications:

HAVING must now be specified before any ORDER BY clause.
The parameters to LOCATE() have been swapped.
There are some new reserved words. The most notable are DATE, TIME, and TIMESTAMP.

4.18.4 Upgrading to Another Architecture

If you are using MySQL Version 3.23, you can copy the .frm, .MYI, and .MYD files between different architectures that support the same floating-point format. (MySQL takes care of any byte swapping issues.)

The MySQL ISAM data and index files (`.ISD' and `*.ISM', respectively) are architecture-dependent and in some cases OS-dependent. If you want to move your applications to another machine that has a different architecture or OS than your current machine, you should not try to move a database by simply copying the files to the other machine. Use mysqldump instead.

By default, mysqldump will create a file full of SQL statements. You can then transfer the file to the other machine and feed it as input to the mysql client.

Try mysqldump --help to see what options are available. If you are moving the data to a newer version of MySQL, you should use mysqldump --opt with the newer version to get a fast, compact dump.

The easiest (although not the fastest) way to move a database between two machines is to run the following commands on the machine on which the database is located:

shell> mysqladmin -h 'other hostname' create db_name
shell> mysqldump --opt db_name \
        | mysql -h 'other hostname' db_name

If you want to copy a database from a remote machine over a slow network, you can use:

shell> mysqladmin create db_name
shell> mysqldump -h 'other hostname' --opt --compress db_name \
        | mysql db_name

You can also store the result in a file, then transfer the file to the target machine and load the file into the database there. For example, you can dump a database to a file on the source machine like this:

shell> mysqldump --quick db_name | gzip > db_name.contents.gz

(The file created in this example is compressed.) Transfer the file containing the database contents to the target machine and run these commands there:

shell> mysqladmin create db_name
shell> gunzip < db_name.contents.gz | mysql db_name

You can also use mysqldump and mysqlimport to accomplish the database transfer. For big tables, this is much faster than simply using mysqldump. In the commands shown below, DUMPDIR represents the full pathname of the directory you use to store the output from mysqldump.

First, create the directory for the output files and dump the database:

shell> mkdir DUMPDIR
shell> mysqldump --tab=DUMPDIR db_name

Then transfer the files in the DUMPDIR directory to some corresponding directory on the target machine and load the files into MySQL there:

shell> mysqladmin create db_name           # create database
shell> cat DUMPDIR/*.sql | mysql db_name   # create tables in database
shell> mysqlimport db_name DUMPDIR/*.txt   # load data into tables

Also, don't forget to copy the mysql database, because that's where the grant tables (user, db, host) are stored. You may have to run commands as the MySQL root user on the new machine until you have the mysql database in place.

After you import the mysql database on the new machine, execute mysqladmin flush-privileges so that the server reloads the grant table information.

5 How Standards-compatible Is MySQL?

This chapter describes how MySQL relates to the ANSI SQL standards. MySQL has many extensions to the ANSI SQL standards, and here you will find out what they are, and how to use them. You will also find information about functionality missing from MySQL, and how to work around some differences.

5.1 MySQL Extensions to ANSI SQL92

MySQL includes some extensions that you probably will not find in other SQL databases. Be warned that if you use them, your code will not be portable to other SQL servers. In some cases, you can write code that includes MySQL extensions, but is still portable, by using comments of the form /*! ... */. In this case, MySQL will parse and execute the code within the comment as it would any other MySQL statement, but other SQL servers will ignore the extensions. For example:

SELECT /*! STRAIGHT_JOIN */ col_name FROM table1,table2 WHERE ...

If you add a version number after the '!', the syntax will only be executed if the MySQL version is equal to or newer than the used version number:

CREATE /*!32302 TEMPORARY */ TABLE (a int);

The above means that if you have Version 3.23.02 or newer, then MySQL will use the TEMPORARY keyword.

MySQL extensions are listed below:

The field types MEDIUMINT, SET, ENUM, and the different BLOB and TEXT types.
The field attributes AUTO_INCREMENT, BINARY, NULL, UNSIGNED, and ZEROFILL.
All string comparisons are case insensitive by default, with sort ordering determined by the current character set (ISO-8859-1 Latin1 by default). If you don't like this, you should declare your columns with the BINARY attribute or use the BINARY cast, which causes comparisons to be done according to the ASCII order used on the MySQL server host.
MySQL maps each database to a directory under the MySQL data directory, and tables within a database to filenames in the database directory. This has a few implications:
- Database names and table names are case sensitive in MySQL on operating systems that have case-sensitive filenames (like most Unix systems). See section 7.1.5.1 Case Sensitivity in Names.
- Database, table, index, column, or alias names may begin with a digit (but may not consist solely of digits).
- You can use standard system commands to backup, rename, move, delete, and copy tables. For example, to rename a table, rename the `.MYD', `.MYI', and `.frm' files to which the table corresponds.
In SQL statements, you can access tables from different databases with the db_name.tbl_name syntax. Some SQL servers provide the same functionality but call this User space. MySQL doesn't support tablespaces as in: create table ralph.my_table...IN my_tablespace.
LIKE is allowed on numeric columns.
Use of INTO OUTFILE and STRAIGHT_JOIN in a SELECT statement. See section 7.19 SELECT Syntax.
The SQL_SMALL_RESULT option in a SELECT statement.
EXPLAIN SELECT to get a description on how tables are joined.
Use of index names, indexes on a prefix of a field, and use of INDEX or KEY in a CREATE TABLE statement. See section 7.7 CREATE TABLE Syntax.
Use of TEMPORARY or IF NOT EXISTS with CREATE TABLE.
Use of COUNT(DISTINCT list) where 'list' is more than one element.
Use of CHANGE col_name, DROP col_name, or DROP INDEX, IGNORE or RENAME in an ALTER TABLE statement. See section 7.8 ALTER TABLE Syntax.
Use of RENAME TABLE. See section 7.9 RENAME TABLE Syntax.
Use of multiple ADD, ALTER, DROP, or CHANGE clauses in an ALTER TABLE statement.
Use of DROP TABLE with the keywords IF EXISTS.
You can drop multiple tables with a single DROP TABLE statement.
The LIMIT clause of the DELETE statement.
The DELAYED clause of the INSERT and REPLACE statements.
The LOW_PRIORITY clause of the INSERT, REPLACE, DELETE, and UPDATE statements.
Use of LOAD DATA INFILE. In many cases, this syntax is compatible with Oracle's LOAD DATA INFILE. See section 7.23 LOAD DATA INFILE Syntax.
The ANALYZE TABLE, CHECK TABLE, OPTIMIZE TABLE, and REPAIR TABLE statements.
The SHOW statement. See section 7.28 SHOW Syntax.
Strings may be enclosed by either `"' or `'', not just by `''.
Use of the escape `\' character.
The SET OPTION statement. See section 7.33 SET Syntax.
You don't need to name all selected columns in the GROUP BY part. This gives better performance for some very specific, but quite normal queries. See section 7.4.13 Functions for Use with GROUP BY Clauses.
One can specify ASC and DESC with GROUP BY.
To make it easier for users who come from other SQL environments, MySQL supports aliases for many functions. For example, all string functions support both ANSI SQL syntax and ODBC syntax.
MySQL understands the || and && operators to mean logical OR and AND, as in the C programming language. In MySQL, || and OR are synonyms, as are && and AND. Because of this nice syntax, MySQL doesn't support the ANSI SQL || operator for string concatenation; use CONCAT() instead. Because CONCAT() takes any number of arguments, it's easy to convert use of the || operator to MySQL.
CREATE DATABASE or DROP DATABASE. See section 7.5 CREATE DATABASE Syntax.
The % operator is a synonym for MOD(). That is, N % M is equivalent to MOD(N,M). % is supported for C programmers and for compatibility with PostgreSQL.
The =, <>, <= ,<, >=,>, <<, >>, <=>, AND, OR, or LIKE operators may be used in column comparisons to the left of the FROM in SELECT statements. For example:
```
mysql> SELECT col1=1 AND col2=2 FROM tbl_name;
```
The LAST_INSERT_ID() function. See section 24.1.3.126 mysql_insert_id().
The REGEXP and NOT REGEXP extended regular expression operators.
CONCAT() or CHAR() with one argument or more than two arguments. (In MySQL, these functions can take any number of arguments.)
The BIT_COUNT(), CASE, ELT(), FROM_DAYS(), FORMAT(), IF(), PASSWORD(), ENCRYPT(), md5(), ENCODE(), DECODE(), PERIOD_ADD(), PERIOD_DIFF(), TO_DAYS(), or WEEKDAY() functions.
Use of TRIM() to trim substrings. ANSI SQL only supports removal of single characters.
The GROUP BY functions STD(), BIT_OR(), and BIT_AND().
Use of REPLACE instead of DELETE + INSERT. See section 7.22 REPLACE Syntax.
The FLUSH flush_option statement.

The possibility to set variables in a statement with :=:

SELECT @a:=SUM(total),@b=COUNT(*),@a/@b AS avg FROM test_table;
SELECT @t1:=(@t2:=1)+@t3:=4,@t1,@t2,@t3;

5.2 Running MySQL in ANSI Mode

If you start mysqld with the --ansi option, the following behavior of MySQL changes:

|| is string concatenation instead of OR.
You can have any number of spaces between a function name and the `('. This forces all function names to be treated as reserved words.
`"' will be an identifier quote character (like the MySQL ``' quote character) and not a string quote character.
REAL will be a synonym for FLOAT instead of a synonym of DOUBLE.
The default transaction isolation level is SERIALIZABLE. See section 7.34 SET TRANSACTION Syntax.

5.3 MySQL Differences Compared to ANSI SQL92

We try to make MySQL follow the ANSI SQL standard and the ODBC SQL standard, but in some cases MySQL does some things differently:

-- is only a comment if followed by a white space. See section 5.4.7 `--' as the Start of a Comment.
For VARCHAR columns, trailing spaces are removed when the value is stored. See section G Known errors and design deficiencies in MySQL.
In some cases, CHAR columns are silently changed to VARCHAR columns. See section 7.7.1 Silent Column Specification Changes.
Privileges for a table are not automatically revoked when you delete a table. You must explicitly issue a REVOKE to revoke privileges for a table. See section 7.35 GRANT and REVOKE Syntax.
NULL AND FALSE will evaluate to NULL and not to FALSE. This is because we don't think it's good to have to evaluate a lot of extra conditions in this case.

5.4 Functionality Missing from MySQL

The following functionality is missing in the current version of MySQL. For a prioritized list indicating when new extensions may be added to MySQL, you should consult the online MySQL TODO list. That is the latest version of the TODO list in this manual. See section H MySQL and the future (The TODO).

5.4.1 Sub-selects

The following will not yet work in MySQL:

SELECT * FROM table1 WHERE id IN (SELECT id FROM table2);
SELECT * FROM table1 WHERE id NOT IN (SELECT id FROM table2);
SELECT * FROM table1 WHERE NOT EXISTS (SELECT id FROM table2 where table1.id=table2.id);

However, in many cases you can rewrite the query without a sub-select:

SELECT table1.* FROM table1,table2 WHERE table1.id=table2.id;
SELECT table1.* FROM table1 LEFT JOIN table2 ON table1.id=table2.id where table2.id IS NULL

For more complicated subqueries you can often create temporary tables to hold the subquery. In some cases, however this option will not work. The most frequently encountered of these cases arises with DELETE statements, for which standard SQL does not support joins (except in sub-selects). For this situation there are two options available until subqueries are supported by MySQL.

The first option is to use a procedural programming language (such as Perl or PHP) to submit a SELECT query to obtain the primary keys for the records to be deleted, and then use these values to construct the DELETE statement (DELETE FROM ... WHERE ... IN (key1, key2, ...)).

The second option is to use interactive SQL to contruct a set of DELETE statements automatically, using the MySQL extension CONCAT() (in lieu of the standard || operator). For example:

SELECT CONCAT('DELETE FROM tab1 WHERE pkid = ', tab1.pkid, ';')
  FROM tab1, tab2
 WHERE tab1.col1 = tab2.col2;

You can place this query in a script file and redirect input from it to the mysql command-line interpreter, piping its output back to a second instance of the interpreter:

prompt> mysql --skip-column-names mydb < myscript.sql | mysql mydb

MySQL only supports INSERT ... SELECT ... and REPLACE ... SELECT ... Independent sub-selects will probably be available in Version 4.0. You can now use the function IN() in other contexts, however.

5.4.2 `SELECT INTO TABLE`

MySQL doesn't yet support the Oracle SQL extension: SELECT ... INTO TABLE .... MySQL supports instead the ANSI SQL syntax INSERT INTO ... SELECT ..., which is basically the same thing. See section 7.21.1 INSERT ... SELECT Syntax.

INSERT INTO tblTemp2 (fldID) SELECT tblTemp1.fldOrder_ID FROM tblTemp1 WHERE
tblTemp1.fldOrder_ID > 100;

Alternatively, you can use SELECT INTO OUTFILE... or CREATE TABLE ... SELECT to solve your problem.

5.4.3 Transactions

As MySQL does nowadays support transactions, the following discussion is only valid if you are only using the non-transaction-safe table types. See section 7.31 BEGIN/COMMIT/ROLLBACK Syntax.

The question is often asked, by the curious and the critical, ``Why is MySQL not a transactional database?'' or ``Why does MySQL not support transactions?''

MySQL has made a conscious decision to support another paradigm for data integrity, ``atomic operations.'' It is our thinking and experience that atomic operations offer equal or even better integrity with much better performance. We, nonetheless, appreciate and understand the transactional database paradigm and plan, within the next few releases, to introduce transaction-safe tables on a per table basis. We will be giving our users the possibility to decide if they need the speed of atomic operations or if they need to use transactional features in their applications.

How does one use the features of MySQL to maintain rigorous integrity and how do these features compare with the transactional paradigm?

First, in the transactional paradigm, if your applications are written in a way that is dependent on the calling of ``rollback'' instead of ``commit'' in critical situations, then transactions are more convenient. Moreover, transactions ensure that unfinished updates or corrupting activities are not committed to the database; the server is given the opportunity to do an automatic rollback and your database is saved.

MySQL, in almost all cases, allows you to solve for potential problems by including simple checks before updates and by running simple scripts that check the databases for inconsistencies and automatically repair or warn if such occurs. Note that just by using the MySQL log or even adding one extra log, one can normally fix tables perfectly with no data integrity loss.

Moreover, fatal transactional updates can be rewritten to be atomic. In fact,we will go so far as to say that all integrity problems that transactions solve can be done with LOCK TABLES or atomic updates, ensuring that you never will get an automatic abort from the database, which is a common problem with transactional databases.

Not even transactions can prevent all loss if the server goes down. In such cases even a transactional system can lose data. The difference between different systems lies in just how small the time-lap is where they could lose data. No system is 100% secure, only ``secure enough.'' Even Oracle, reputed to be the safest of transactional databases, is reported to sometimes lose data in such situations.

To be safe with MySQL, you only need to have backups and have the update logging turned on. With this you can recover from any situation that you could with any transactional database. It is, of course, always good to have backups, independent of which database you use.

The transactional paradigm has its benefits and its drawbacks. Many users and application developers depend on the ease with which they can code around problems where an abort appears to be, or is necessary, and they may have to do a little more work with MySQL to either think differently or write more. If you are new to the atomic operations paradigm, or more familiar or more comfortable with transactions, do not jump to the conclusion that MySQL has not addressed these issues. Reliability and integrity are foremost in our minds. Recent estimates indicate that there are more than 1,000,000 mysqld servers currently running, many of which are in production environments. We hear very, very seldom from our users that they have lost any data, and in almost all of those cases user error is involved. This is, in our opinion, the best proof of MySQL's stability and reliability.

Lastly, in situations where integrity is of highest importance, MySQL's current features allow for transaction-level or better reliability and integrity. If you lock tables with LOCK TABLES, all updates will stall until any integrity checks are made. If you only obtain a read lock (as opposed to a write lock), then reads and inserts are still allowed to happen. The new inserted records will not be seen by any of the clients that have a READ lock until they release their read locks. With INSERT DELAYED you can queue inserts into a local queue, until the locks are released, without having the client wait for the insert to complete. See section 7.21.2 INSERT DELAYED syntax.

``Atomic,'' in the sense that we mean it, is nothing magical. It only means that you can be sure that while each specific update is running, no other user can interfere with it, and there will never be an automatic rollback (which can happen on transaction based systems if you are not very careful). MySQL also guarantees that there will not be any dirty reads. You can find some example of how to write atomic updates in the commit-rollback section. See section 5.6 How to Cope Without COMMIT/ROLLBACK.

We have thought quite a bit about integrity and performance, and we believe that our atomic operations paradigm allows for both high reliability and extremely high performance, on the order of three to five times the speed of the fastest and most optimally tuned of transactional databases. We didn't leave out transactions because they are hard to do. The main reason we went with atomic operations as opposed to transactions is that by doing this we could apply many speed optimizations that would not otherwise have been possible.

Many of our users who have speed foremost in their minds are not at all concerned about transactions. For them transactions are not an issue. For those of our users who are concerned with or have wondered about transactions vis-a-vis MySQL, there is a ``MySQL way'' as we have outlined above. For those where safety is more important than speed, we recommend them to use the BDB, GEMINI or InnoDB tables for all their critical data. See section 8 MySQL Table Types.

One final note: We are currently working on a safe replication schema that we believe to be better than any commercial replication system we know of. This system will work most reliably under the atomic operations, non-transactional, paradigm. Stay tuned.

5.4.4 Stored Procedures and Triggers

A stored procedure is a set of SQL commands that can be compiled and stored in the server. Once this has been done, clients don't need to keep reissuing the entire query but can refer to the stored procedure. This provides better performance because the query has to be parsed only once, and less information needs to be sent between the server and the client. You can also raise the conceptual level by having libraries of functions in the server.

A trigger is a stored procedure that is invoked when a particular event occurs. For example, you can install a stored procedure that is triggered each time a record is deleted from a transaction table and that automatically deletes the corresponding customer from a customer table when all his transactions are deleted.

The planned update language will be able to handle stored procedures, but without triggers. Triggers usually slow down everything, even queries for which they are not needed.

To see when MySQL might get stored procedures, see section H MySQL and the future (The TODO).

5.4.5 Foreign Keys

Note that foreign keys in SQL are not used to join tables, but are used mostly for checking referential integrity (foreign key constraints). If you want to get results from multiple tables from a SELECT statement, you do this by joining tables:

SELECT * from table1,table2 where table1.id = table2.id;

See section 7.20 JOIN Syntax. See section 9.5.6 Using Foreign Keys.

The FOREIGN KEY syntax in MySQL exists only for compatibility with other SQL vendors' CREATE TABLE commands; it doesn't do anything. The FOREIGN KEY syntax without ON DELETE ... is mostly used for documentation purposes. Some ODBC applications may use this to produce automatic WHERE clauses, but this is usually easy to override. FOREIGN KEY is sometimes used as a constraint check, but this check is unnecessary in practice if rows are inserted into the tables in the right order. MySQL only supports these clauses because some applications require them to exist (regardless of whether or not they work).

In MySQL, you can work around the problem of ON DELETE ... not being implemented by adding the appropriate DELETE statement to an application when you delete records from a table that has a foreign key. In practice this is as quick (in some cases quicker) and much more portable than using foreign keys.

In the near future we will extend the FOREIGN KEY implementation so that at least the information will be saved in the table specification file and may be retrieved by mysqldump and ODBC. At a later stage we will implement the foreign key constraints for application that can't easily be coded to avoid them.

5.4.5.1 Reasons NOT to Use Foreign Keys constraints

There are so many problems with foreign key constraints that we don't know where to start:

Foreign key constraints make life very complicated, because the foreign key definitions must be stored in a database and implementing them would destroy the whole ``nice approach'' of using files that can be moved, copied, and removed.
The speed impact is terrible for INSERT and UPDATE statements, and in this case almost all FOREIGN KEY constraint checks are useless because you usually insert records in the right tables in the right order, anyway.
There is also a need to hold locks on many more tables when updating one table, because the side effects can cascade through the entire database. It's MUCH faster to delete records from one table first and subsequently delete them from the other tables.
You can no longer restore a table by doing a full delete from the table and then restoring all records (from a new source or from a backup).
If you use foreign key constraints you can't dump and restore tables unless you do so in a very specific order.
It's very easy to do ``allowed'' circular definitions that make the tables impossible to re-create each table with a single create statement, even if the definition works and is usable.
It's very easy to overlook FOREIGN KEY ... ON DELETE rules when one codes an application. It's not unusual that one loses a lot of important information just because a wrong or misused ON DELETE rule.

The only nice aspect of FOREIGN KEY is that it gives ODBC and some other client programs the ability to see how a table is connected and to use this to show connection diagrams and to help in building applications.

MySQL will soon store FOREIGN KEY definitions so that a client can ask for and receive an answer about how the original connection was made. The current `.frm' file format does not have any place for it. At a later stage we will implement the foreign key constraints for application that can't easily be coded to avoid them.

5.4.6 Views

MySQL doesn't yet support views, but we plan to implement these to about 4.1.

Views are mostly useful for letting users access a set of relations as one table (in read-only mode). Many SQL databases don't allow one to update any rows in a view, but you have to do the updates in the separate tables.

As MySQL is mostly used in applications and on web system where the application writer has full control on the database usage, most of our users haven't regarded views to be very important. (At least no one has been interested enough in this to be prepared to finance the implementation of views).

One doesn't need views in MySQL to restrict access to columns as MySQL has a very sophisticated privilege system. See section 6 The MySQL Access Privilege System.

5.4.7 `--' as the Start of a Comment

Some other SQL databases use `--' to start comments. MySQL has `#' as the start comment character, even if the mysql command-line tool removes all lines that start with `--'. You can also use the C comment style /* this is a comment */ with MySQL. See section 7.38 Comment Syntax.

MySQL Version 3.23.3 and above supports the `--' comment style only if the comment is followed by a space. This is because this degenerate comment style has caused many problems with automatically generated SQL queries that have used something like the following code, where we automatically insert the value of the payment for !payment!:

UPDATE tbl_name SET credit=credit-!payment!

What do you think will happen when the value of payment is negative?

Because 1--1 is legal in SQL, we think it is terrible that `--' means start comment.

In MySQL Version 3.23 you can, however, use: 1-- This is a comment

The following discussion only concerns you if you are running a MySQL version earlier than Version 3.23:

If you have a SQL program in a text file that contains `--' comments you should use:

shell> replace " --" " #" < text-file-with-funny-comments.sql \
         | mysql database

instead of the usual:

shell> mysql database < text-file-with-funny-comments.sql

You can also edit the command file ``in place'' to change the `--' comments to `#' comments:

shell> replace " --" " #" -- text-file-with-funny-comments.sql

Change them back with this command:

shell> replace " #" " --" -- text-file-with-funny-comments.sql

5.5 What Standards Does MySQL Follow?

Entry level SQL92. ODBC levels 0-2.

5.6 How to Cope Without `COMMIT`/`ROLLBACK`

The following mostly applies only for ISAM, MyISAM, and HEAP tables. If you only use transaction-safe tables (BDB, GEMINI or InnoDB tables) in an an update, you can do COMMIT and ROLLBACK also with MySQL. See section 7.31 BEGIN/COMMIT/ROLLBACK Syntax.

The problem with handling COMMIT-ROLLBACK efficiently with the above table types would require a completely different table layout than MySQL uses today. The table type would also need extra threads that do automatic cleanups on the tables, and the disk usage would be much higher. This would make these table types about 2-4 times slower than they are today.

For the moment, we prefer implementing the SQL server language (something like stored procedures). With this you would very seldom really need COMMIT-ROLLBACK. This would also give much better performance.

Loops that need transactions normally can be coded with the help of LOCK TABLES, and you don't need cursors when you can update records on the fly.

We at TcX had a greater need for a real fast database than a 100% general database. Whenever we find a way to implement these features without any speed loss, we will probably do it. For the moment, there are many more important things to do. Check the TODO for how we prioritize things at the moment. (Customers with higher levels of support can alter this, so things may be reprioritized.)

The current problem is actually ROLLBACK. Without ROLLBACK, you can do any kind of COMMIT action with LOCK TABLES. To support ROLLBACK with the above table types, MySQL would have to be changed to store all old records that were updated and revert everything back to the starting point if ROLLBACK was issued. For simple cases, this isn't that hard to do (the current isamlog could be used for this purpose), but it would be much more difficult to implement ROLLBACK for ALTER/DROP/CREATE TABLE.

To avoid using ROLLBACK, you can use the following strategy:

Use LOCK TABLES ... to lock all the tables you want to access.
Test conditions.
Update if everything is okay.
Use UNLOCK TABLES to release your locks.

This is usually a much faster method than using transactions with possible ROLLBACKs, although not always. The only situation this solution doesn't handle is when someone kills the threads in the middle of an update. In this case, all locks will be released but some of the updates may not have been executed.

You can also use functions to update records in a single operation. You can get a very efficient application by using the following techniques:

Modify fields relative to their current value.
Update only those fields that actually have changed.

For example, when we are doing updates to some customer information, we update only the customer data that has changed and test only that none of the changed data, or data that depend on the changed data, has changed compared to the original row. The test for changed data is done with the WHERE clause in the UPDATE statement. If the record wasn't updated, we give the client a message: "Some of the data you have changed have been changed by another user". Then we show the old row versus the new row in a window, so the user can decide which version of the customer record he should use.

This gives us something that is similar to column locking but is actually even better, because we only update some of the columns, using values that are relative to their current values. This means that typical UPDATE statements look something like these:

UPDATE tablename SET pay_back=pay_back+'relative change';

UPDATE customer
  SET
    customer_date='current_date',
    address='new address',
    phone='new phone',
    money_he_owes_us=money_he_owes_us+'new_money'
  WHERE
    customer_id=id AND address='old address' AND phone='old phone';

As you can see, this is very efficient and works even if another client has changed the values in the pay_back or money_he_owes_us columns.

In many cases, users have wanted ROLLBACK and/or LOCK TABLES for the purpose of managing unique identifiers for some tables. This can be handled much more efficiently by using an AUTO_INCREMENT column and either the SQL function LAST_INSERT_ID() or the C API function mysql_insert_id(). See section 24.1.3.126 mysql_insert_id().

At MySQL AB, we have never had any need for row-level locking because we have always been able to code around it. Some cases really need row locking, but they are very few. If you want row-level locking, you can use a flag column in the table and do something like this:

UPDATE tbl_name SET row_flag=1 WHERE id=ID;

MySQL returns 1 for the number of affected rows if the row was found and row_flag wasn't already 1 in the original row.

You can think of it as MySQL changed the above query to:

UPDATE tbl_name SET row_flag=1 WHERE id=ID and row_flag <> 1;

6 The MySQL Access Privilege System

MySQL has an advanced but non-standard security/privilege system. This section describes how it works.

6.1 General Security

Anyone using MySQL on a computer connected to the Internet should read this section to avoid the most common security mistakes.

In discussing security, we emphasize the necessity of fully protecting the entire server host (not simply the MySQL server) against all types of applicable attacks: eavesdropping, altering, playback, and denial of service. We do not cover all aspects of availability and fault tolerance here.

MySQL uses security based on Access Control Lists (ACLs) for all connections, queries, and other operations that a user may attempt to perform. There is also some support for SSL-encrypted connections between MySQL clients and servers. Many of the concepts discussed here are not specific to MySQL at all; the same general ideas apply to almost all applications.

When running MySQL, follow these guidelines whenever possible:

DON'T EVER GIVE ANYONE (EXCEPT THE MySQL ROOT USER) ACCESS TO THE mysql.user TABLE! The encrypted password is the real password in MySQL. If you know this for one user, you can easily log in as him if you have access to his 'host'.
Learn the MySQL access privilege system. The GRANT and REVOKE commands are used for controlling access to MySQL. Do not grant any more privileges than necessary. Never grant privileges to all hosts. Checklist:
- Try mysql -u root. If you are able to connect successfully to the server without being asked for a password, you have problems. Anyone can connect to your MySQL server as the MySQL root user with full privileges! Review the MySQL installation instructions, paying particular attention to the item about setting a root password.
- Use the command SHOW GRANTS and check to see who has access to what. Remove those privileges that are not necessary using the REVOKE command.
Do not keep any plain-text passwords in your database. When your computer becomes compromised, the intruder can take the full list of passwords and use them. Instead use MD5() or another one-way hashing function.
Do not use passwords from dictionaries. There are special programs to break them. Even passwords like ``xfish98'' are very bad. Much better is ``duag98'' which contains the same word ``fish'' but typed one key to the left on a standard QWERTY keyboard. Another method is to use ``Mhall'' which is taken from the first characters of each word in the sentence ``Mary had a little lamb.'' This is easy to remember and type, but hard to guess for someone who does not know it.
Invest in a firewall. This protects from at least 50% of all types of exploits in any software. Put MySQL behind the firewall or in a demilitarized zone (DMZ). Checklist:
- Try to scan your ports from the Internet using a tool such as nmap. MySQL uses port 3306 by default. This port should be inaccessible from untrusted hosts. Another simple way to check whether or not your MySQL port is open is to type telnet server_host 3306 from some remote machine, where server_host is the hostname of your MySQL server. If you get a connection and some garbage characters, the port is open, and should be closed on your firewall or router, unless you really have a good reason to keep it open. If telnet just hangs or the connection is refused, everything is OK; the port is blocked.
Do not trust any data entered by your users. They can try to trick your code by entering special or escaped character sequences in Web forms, URLs, or whatever application you have built. Be sure that your application remains secure if a user enters something like ``; DROP DATABASE mysql;''. This is an extreme example, but large security leaks and data loss may occur as a result of hackers using similar techniques, if you do not prepare for them. Also remember to check numeric data. A common mistake is to protect only strings. Sometimes people think that if a database contains only publicly available data that it need not be protected. This is incorrect. At least denial-of-service type attacks can be performed on such databases. The simplest way to protect from this type of attack is to use apostrophes around the numeric constants: SELECT * FROM table WHERE ID='234' rather than SELECT * FROM table WHERE ID=234. MySQL automatically converts this string to a number and strips all non-numeric symbols from it. Checklist:
- All Web applications:
  - Try to enter `'' and `"' in all your Web forms. If you get any kind of MySQL error, investigate the problem right away.
  - Try to modify any dynamic URLs by adding %22 (`"'), %23 (`#'), and %27 (`'') in the URL.
  - Try to modify datatypes in dynamic URLs from numeric ones to character ones containing characters from previous examples. Your application should be safe against this and similar attacks.
  - Try to enter characters, spaces, and special symbols instead of numbers in numeric fields. Your application should remove them before passing them to MySQL or your application should generate an error. Passing unchecked values to MySQL is very dangerous!
  - Check data sizes before passing them to MySQL.
  - Consider having your application connect to the database using a different user name than the one you use for administrative purposes. Do not give your applications any more access privileges than they need.
- Users of PHP:
  - Check out the addslashes() function.
- Users of MySQL C API:
  - Check out the mysql_escape() API call.
- Users of MySQL++:
  - Check out the escape and quote modifiers for query streams.
- Users of Perl DBI:
  - Check out the quote() method or use placeholders.
Do not transmit plain (unencrypted) data over the Internet. These data are accessible to everyone who has the time and ability to intercept it and use it for their own purposes. Instead, use an encrypted protocol such as SSL or SSH. MySQL supports internal SSL connections as of Version 3.23.9. SSH port-forwarding can be used to create an encrypted (and compressed) tunnel for the communication.
Learn to use the tcpdump and strings utilities. For most cases, you can check whether or not MySQL data streams are unencrypted by issuing a command like the following:
```
shell> tcpdump -l -i eth0 -w - src or dst port 3306 | strings
```
(This works under Linux and should work with small modifications under other systems). Warning: If you do not see data this doesn't always actually mean that it is encrypted. If you need high security, you should consult with a security expert.

6.2 How to Make MySQL Secure Against Crackers

When you connect to a MySQL server, you normally should use a password. The password is not transmitted in clear text over the connection, however the encryption algorithm is not very strong, and with some effort a clever attacker can crack the password if he is able to sniff the traffic between the client and the server. If the connection between the client and the server goes through an untrusted network, you should use an SSH tunnel to encrypt the communication.

All other information is transferred as text that can be read by anyone who is able to watch the connection. If you are concerned about this, you can use the compressed protocol (in MySQL Version 3.22 and above) to make things much harder. To make things even more secure you should use ssh (see http://www.cs.hut.fi/ssh). With this, you can get an encrypted TCP/IP connection between a MySQL server and a MySQL client.

To make a MySQL system secure, you should strongly consider the following suggestions:

Use passwords for all MySQL users. Remember that anyone can log in as any other person as simply as mysql -u other_user db_name if other_user has no password. It is common behavior with client/server applications that the client may specify any user name. You can change the password of all users by editing the mysql_install_db script before you run it, or only the password for the MySQL root user like this:
```
shell> mysql -u root mysql
mysql> UPDATE user SET Password=PASSWORD('new_password')
           WHERE user='root';
mysql> FLUSH PRIVILEGES;
```
Don't run the MySQL daemon as the Unix root user. It is very dangerous as any user with FILE privileges will be able to create files as root (for example, ~root/.bashrc). To prevent this mysqld will refuse to run as root unless it is specified directly via --user=root option. mysqld can be run as any user instead. You can also create a new Unix user mysql to make everything even more secure. If you run mysqld as another Unix user, you don't need to change the root user name in the user table, because MySQL user names have nothing to do with Unix user names. You can edit the mysql.server script to start mysqld as another Unix user. Normally this is done with the su command. For more details, see section 21.9 How to Run MySQL As a Normal User.
If you put a password for the Unix root user in the mysql.server script, make sure this script is readable only by root.
Check that the Unix user that mysqld runs as is the only user with read/write privileges in the database directories.
On Unix platforms, do not run mysqld as root unless you really need to. Consider creating a user named mysql for that purpose.
Don't give the process privilege to all users. The output of mysqladmin processlist shows the text of the currently executing queries, so any user who is allowed to execute that command might be able to see if another user issues an UPDATE user SET password=PASSWORD('not_secure') query. mysqld reserves an extra connection for users who have the process privilege, so that a MySQL root user can log in and check things even if all normal connections are in use.
Don't give the file privilege to all users. Any user that has this privilege can write a file anywhere in the file system with the privileges of the mysqld daemon! To make this a bit safer, all files generated with SELECT ... INTO OUTFILE are readable to everyone, and you cannot overwrite existing files. The file privilege may also be used to read any file accessible to the Unix user that the server runs as. This could be abused, for example, by using LOAD DATA to load `/etc/passwd' into a table, which can then be read with SELECT.
If you don't trust your DNS, you should use IP numbers instead of hostnames in the grant tables. In principle, the --secure option to mysqld should make hostnames safe. In any case, you should be very careful about creating grant table entries using hostname values that contain wild cards!
If you want to restrict the number of connections for a single user, you can do this by setting the max_user_connections variable in mysqld.

6.3 Startup Options for `mysqld` Concerning Security

The following mysqld options affect networking security:

--secure: IP numbers returned by the gethostbyname() system call are checked to make sure they resolve back to the original hostname. This makes it harder for someone on the outside to get access by pretending to be another host. This option also adds some sanity checks of hostnames. The option is turned off by default in MySQL Version 3.21 because sometimes it takes a long time to perform backward resolutions. MySQL Version 3.22 caches hostnames and has this option enabled by default.
--skip-grant-tables: This option causes the server not to use the privilege system at all. This gives everyone full access to all databases! (You can tell a running server to start using the grant tables again by executing mysqladmin flush-privileges or mysqladmin reload.)
--skip-name-resolve: Hostnames are not resolved. All Host column values in the grant tables must be IP numbers or localhost.
--skip-networking: Don't allow TCP/IP connections over the network. All connections to mysqld must be made via Unix sockets. This option is unsuitable for systems that use MIT-pthreads, because the MIT-pthreads package doesn't support Unix sockets.
--skip-show-database: With this option, the SHOW DATABASES statement doesn't return anything.
--safe-show-database: With this option, SHOW DATABASES returns only those databases for which the user has some kind of privilege.

6.4 What the Privilege System Does

The primary function of the MySQL privilege system is to authenticate a user connecting from a given host, and to associate that user with privileges on a database such as select, insert, update and delete.

Additional functionality includes the ability to have an anonymous user and to grant privileges for MySQL-specific functions such as LOAD DATA INFILE and administrative operations.

6.5 MySQL User Names and Passwords

There are several distinctions between the way user names and passwords are used by MySQL and the way they are used by Unix or Windows:

User names, as used by MySQL for authentication purposes, have nothing to do with Unix user names (login names) or Windows user names. Most MySQL clients by default try to log in using the current Unix user name as the MySQL user name, but that is for convenience only. Client programs allow a different name to be specified with the -u or --user options. This means that you can't make a database secure in any way unless all MySQL user names have passwords. Anyone may attempt to connect to the server using any name, and they will succeed if they specify any name that doesn't have a password.
MySQL user names can be up to 16 characters long; Unix user names typically are limited to 8 characters.
MySQL passwords have nothing to do with Unix passwords. There is no necessary connection between the password you use to log in to a Unix machine and the password you use to access a database on that machine.
MySQL encrypts passwords using a different algorithm than the one used during the Unix login process. See the descriptions of the PASSWORD() and ENCRYPT() functions in section 7.4.12 Miscellaneous Functions. Note that even if the password is stored 'scrambled', and knowing your 'scrambled' password is enough to be able to connect to the MySQL server!

6.6 Connecting to the MySQL Server

MySQL client programs generally require that you specify connection parameters when you want to access a MySQL server: the host you want to connect to, your user name, and your password. For example, the mysql client can be started like this (optional arguments are enclosed between `[' and `]'):

shell> mysql [-h host_name] [-u user_name] [-pyour_pass]

Alternate forms of the -h, -u, and -p options are --host=host_name, --user=user_name, and --password=your_pass. Note that there is no space between -p or --password= and the password following it.

NOTE: Specifying a password on the command line is not secure! Any user on your system may then find out your password by typing a command like: ps auxww. See section 4.16.5 Option Files.

mysql uses default values for connection parameters that are missing from the command line:

The default hostname is localhost.
The default user name is your Unix login name.
No password is supplied if -p is missing.

Thus, for a Unix user joe, the following commands are equivalent:

shell> mysql -h localhost -u joe
shell> mysql -h localhost
shell> mysql -u joe
shell> mysql

Other MySQL clients behave similarly.

On Unix systems, you can specify different default values to be used when you make a connection, so that you need not enter them on the command line each time you invoke a client program. This can be done in a couple of ways:

You can specify connection parameters in the [client] section of the `.my.cnf' configuration file in your home directory. The relevant section of the file might look like this:
```
[client]
host=host_name
user=user_name
password=your_pass
```
See section 4.16.5 Option Files.
You can specify connection parameters using environment variables. The host can be specified for mysql using MYSQL_HOST. The MySQL user name can be specified using USER (this is for Windows only). The password can be specified using MYSQL_PWD (but this is insecure; see the next section). See section A Environment Variables.

6.7 Keeping Your Password Secure

It is inadvisable to specify your password in a way that exposes it to discovery by other users. The methods you can use to specify your password when you run client programs are listed below, along with an assessment of the risks of each method:

Never give a normal user access to the mysql.user table. Knowing the encrypted password for a user makes it possible to login as this user. The passwords are only scrambled so that one shouldn't be able to see the real password you used (if you happen to use a similar password with your other applications).
Use a -pyour_pass or --password=your_pass option on the command line. This is convenient but insecure, because your password becomes visible to system status programs (such as ps) that may be invoked by other users to display command lines. (MySQL clients typically overwrite the command-line argument with zeroes during their initialization sequence, but there is still a brief interval during which the value is visible.)
Use a -p or --password option (with no your_pass value specified). In this case, the client program solicits the password from the terminal:
```
shell> mysql -u user_name -p
Enter password: ********
```
The `*' characters represent your password. It is more secure to enter your password this way than to specify it on the command line because it is not visible to other users. However, this method of entering a password is suitable only for programs that you run interactively. If you want to invoke a client from a script that runs non-interactively, there is no opportunity to enter the password from the terminal. On some systems, you may even find that the first line of your script is read and interpreted (incorrectly) as your password!
Store your password in a configuration file. For example, you can list your password in the [client] section of the `.my.cnf' file in your home directory:
```
[client]
password=your_pass
```
If you store your password in `.my.cnf', the file should not be group or world readable or writable. Make sure the file's access mode is 400 or 600. See section 4.16.5 Option Files.
You can store your password in the MYSQL_PWD environment variable, but this method must be considered extremely insecure and should not be used. Some versions of ps include an option to display the environment of running processes; your password will be in plain sight for all to see if you set MYSQL_PWD. Even on systems without such a version of ps, it is unwise to assume there is no other method to observe process environments. See section A Environment Variables.

All in all, the safest methods are to have the client program prompt for the password or to specify the password in a properly protected `.my.cnf' file.

6.8 Privileges Provided by MySQL

Information about user privileges is stored in the user, db, host, tables_priv, and columns_priv tables in the mysql database (that is, in the database named mysql). The MySQL server reads the contents of these tables when it starts up and under the circumstances indicated in section 6.12 When Privilege Changes Take Effect.

The names used in this manual to refer to the privileges provided by MySQL are shown below, along with the table column name associated with each privilege in the grant tables and the context in which the privilege applies:

Privilege	Column	Context
select	`Select_priv`	tables
insert	`Insert_priv`	tables
update	`Update_priv`	tables
delete	`Delete_priv`	tables
index	`Index_priv`	tables
alter	`Alter_priv`	tables
create	`Create_priv`	databases, tables, or indexes
drop	`Drop_priv`	databases or tables
grant	`Grant_priv`	databases or tables
references	`References_priv`	databases or tables
reload	`Reload_priv`	server administration
shutdown	`Shutdown_priv`	server administration
process	`Process_priv`	server administration
file	`File_priv`	file access on server

The select, insert, update, and delete privileges allow you to perform operations on rows in existing tables in a database.

SELECT statements require the select privilege only if they actually retrieve rows from a table. You can execute certain SELECT statements even without permission to access any of the databases on the server. For example, you could use the mysql client as a simple calculator:

mysql> SELECT 1+1;
mysql> SELECT PI()*2;

The index privilege allows you to create or drop (remove) indexes.

The alter privilege allows you to use ALTER TABLE.

The create and drop privileges allow you to create new databases and tables, or to drop (remove) existing databases and tables.

Note that if you grant the drop privilege for the mysql database to a user, that user can drop the database in which the MySQL access privileges are stored!

The grant privilege allows you to give to other users those privileges you yourself possess.

The file privilege gives you permission to read and write files on the server using the LOAD DATA INFILE and SELECT ... INTO OUTFILE statements. Any user to whom this privilege is granted can read or write any file that the MySQL server can read or write.

The remaining privileges are used for administrative operations, which are performed using the mysqladmin program. The table below shows which mysqladmin commands each administrative privilege allows you to execute:

Privilege	Commands permitted to privilege holders
reload	`reload`, `refresh`, `flush-privileges`, `flush-hosts`, `flush-logs`, and `flush-tables`
shutdown	`shutdown`
process	`processlist`, `kill`

The reload command tells the server to re-read the grant tables. The refresh command flushes all tables and opens and closes the log files. flush-privileges is a synonym for reload. The other flush-* commands perform functions similar to refresh but are more limited in scope, and may be preferable in some instances. For example, if you want to flush just the log files, flush-logs is a better choice than refresh.

The shutdown command shuts down the server.

The processlist command displays information about the threads executing within the server. The kill command kills server threads. You can always display or kill your own threads, but you need the process privilege to display or kill threads initiated by other users. See section 7.27 KILL Syntax.

It is a good idea in general to grant privileges only to those users who need them, but you should exercise particular caution in granting certain privileges:

The grant privilege allows users to give away their privileges to other users. Two users with different privileges and with the grant privilege are able to combine privileges.
The alter privilege may be used to subvert the privilege system by renaming tables.
The file privilege can be abused to read any world-readable file on the server into a database table, the contents of which can then be accessed using SELECT. This includes the contents of all databases hosted by the server!
The shutdown privilege can be abused to deny service to other users entirely, by terminating the server.
The process privilege can be used to view the plain text of currently executing queries, including queries that set or change passwords.
Privileges on the mysql database can be used to change passwords and other access privilege information. (Passwords are stored encrypted, so a malicious user cannot simply read them to know the plain text password). If they can access the mysql.user password column, they can use it to log into the MySQL server for the given user. (With sufficient privileges, the same user can replace a password with a different one.)

There are some things that you cannot do with the MySQL privilege system:

You cannot explicitly specify that a given user should be denied access. That is, you cannot explicitly match a user and then refuse the connection.
You cannot specify that a user has privileges to create or drop tables in a database but not to create or drop the database itself.

6.9 How the Privilege System Works

The MySQL privilege system ensures that all users may do exactly the things that they are supposed to be allowed to do. When you connect to a MySQL server, your identity is determined by the host from which you connect and the user name you specify. The system grants privileges according to your identity and what you want to do.

MySQL considers both your hostname and user name in identifying you because there is little reason to assume that a given user name belongs to the same person everywhere on the Internet. For example, the user bill who connects from whitehouse.gov need not be the same person as the user bill who connects from microsoft.com. MySQL handles this by allowing you to distinguish users on different hosts that happen to have the same name: you can grant bill one set of privileges for connections from whitehouse.gov, and a different set of privileges for connections from microsoft.com.

MySQL access control involves two stages:

Stage 1: The server checks whether or not you are even allowed to connect.
Stage 2: Assuming you can connect, the server checks each request you issue to see whether or not you have sufficient privileges to perform it. For example, if you try to select rows from a table in a database or drop a table from the database, the server makes sure you have the select privilege for the table or the drop privilege for the database.

The server uses the user, db, and host tables in the mysql database at both stages of access control. The fields in these grant tables are shown below:

Table name	`user`	`db`	`host`
Scope fields	`Host`	`Host`	`Host`
	`User`	`Db`	`Db`
	`Password`	`User`
Privilege fields	`Select_priv`	`Select_priv`	`Select_priv`
	`Insert_priv`	`Insert_priv`	`Insert_priv`
	`Update_priv`	`Update_priv`	`Update_priv`
	`Delete_priv`	`Delete_priv`	`Delete_priv`
	`Index_priv`	`Index_priv`	`Index_priv`
	`Alter_priv`	`Alter_priv`	`Alter_priv`
	`Create_priv`	`Create_priv`	`Create_priv`
	`Drop_priv`	`Drop_priv`	`Drop_priv`
	`Grant_priv`	`Grant_priv`	`Grant_priv`
	`References_priv`
	`Reload_priv`
	`Shutdown_priv`
	`Process_priv`
	`File_priv`

For the second stage of access control (request verification), the server may, if the request involves tables, additionally consult the tables_priv and columns_priv tables. The fields in these tables are shown below:

Table name	`tables_priv`	`columns_priv`
Scope fields	`Host`	`Host`
	`Db`	`Db`
	`User`	`User`
	`Table_name`	`Table_name`
		`Column_name`
Privilege fields	`Table_priv`	`Column_priv`
	`Column_priv`
Other fields	`Timestamp`	`Timestamp`
	`Grantor`

Each grant table contains scope fields and privilege fields.

Scope fields determine the scope of each entry in the tables, that is, the context in which the entry applies. For example, a user table entry with Host and User values of 'thomas.loc.gov' and 'bob' would be used for authenticating connections made to the server by bob from the host thomas.loc.gov. Similarly, a db table entry with Host, User, and Db fields of 'thomas.loc.gov', 'bob' and 'reports' would be used when bob connects from the host thomas.loc.gov to access the reports database. The tables_priv and columns_priv tables contain scope fields indicating tables or table/column combinations to which each entry applies.

For access-checking purposes, comparisons of Host values are case insensitive. User, Password, Db, and Table_name values are case sensitive. Column_name values are case insensitive in MySQL Version 3.22.12 or later.

Privilege fields indicate the privileges granted by a table entry, that is, what operations can be performed. The server combines the information in the various grant tables to form a complete description of a user's privileges. The rules used to do this are described in section 6.11 Access Control, Stage 2: Request Verification.

Scope fields are strings, declared as shown below; the default value for each is the empty string:

Field name	Type
`Host`	`CHAR(60)`
`User`	`CHAR(16)`
`Password`	`CHAR(16)`
`Db`	`CHAR(64)`	(`CHAR(60)` for the `tables_priv` and `columns_priv` tables)
`Table_name`	`CHAR(60)`
`Column_name`	`CHAR(60)`

In the user, db and host tables, all privilege fields are declared as ENUM('N','Y') -- each can have a value of 'N' or 'Y', and the default value is 'N'.

In the tables_priv and columns_priv tables, the privilege fields are declared as SET fields:

Table name	Field name	Possible set elements
`tables_priv`	`Table_priv`	`'Select', 'Insert', 'Update', 'Delete', 'Create', 'Drop', 'Grant', 'References', 'Index', 'Alter'`
`tables_priv`	`Column_priv`	`'Select', 'Insert', 'Update', 'References'`
`columns_priv`	`Column_priv`	`'Select', 'Insert', 'Update', 'References'`

Briefly, the server uses the grant tables like this:

The user table scope fields determine whether to allow or reject incoming connections. For allowed connections, any privileges granted in the user table indicate the user's global (superuser) privileges. These privileges apply to all databases on the server.
The db and host tables are used together:
- The db table scope fields determine which users can access which databases from which hosts. The privilege fields determine which operations are allowed.
- The host table is used as an extension of the db table when you want a given db table entry to apply to several hosts. For example, if you want a user to be able to use a database from several hosts in your network, leave the Host value empty in the user's db table entry, then populate the host table with an entry for each of those hosts. This mechanism is described more detail in section 6.11 Access Control, Stage 2: Request Verification.
The tables_priv and columns_priv tables are similar to the db table, but are more fine-grained: they apply at the table and column levels rather than at the database level.

Note that administrative privileges (reload, shutdown, etc.) are specified only in the user table. This is because administrative operations are operations on the server itself and are not database-specific, so there is no reason to list such privileges in the other grant tables. In fact, only the user table need be consulted to determine whether or not you can perform an administrative operation.

The file privilege is specified only in the user table, too. It is not an administrative privilege as such, but your ability to read or write files on the server host is independent of the database you are accessing.

The mysqld server reads the contents of the grant tables once, when it starts up. Changes to the grant tables take effect as indicated in section 6.12 When Privilege Changes Take Effect.

When you modify the contents of the grant tables, it is a good idea to make sure that your changes set up privileges the way you want. For help in diagnosing problems, see section 6.16 Causes of Access denied Errors. For advice on security issues, see section 6.2 How to Make MySQL Secure Against Crackers.

A useful diagnostic tool is the mysqlaccess script, which Yves Carlier has provided for the MySQL distribution. Invoke mysqlaccess with the --help option to find out how it works. Note that mysqlaccess checks access using only the user, db and host tables. It does not check table- or column-level privileges.

6.10 Access Control, Stage 1: Connection Verification

When you attempt to connect to a MySQL server, the server accepts or rejects the connection based on your identity and whether or not you can verify your identity by supplying the correct password. If not, the server denies access to you completely. Otherwise, the server accepts the connection, then enters Stage 2 and waits for requests.

Your identity is based on two pieces of information:

The host from which you connect
Your MySQL user name

Identity checking is performed using the three user table scope fields (Host, User, and Password). The server accepts the connection only if a user table entry matches your hostname and user name, and you supply the correct password.

Values in the user table scope fields may be specified as follows:

A Host value may be a hostname or an IP number, or 'localhost' to indicate the local host.
You can use the wild-card characters `%' and `_' in the Host field.
A Host value of '%' matches any hostname.
A blank Host value means that the privilege should be anded with the entry in the host table that matches the given host name. You can find more information about this in the next chapter.
As of MySQL Version 3.23, for Host values specified as IP numbers, you can specify a netmask indicating how many address bits to use for the network number. For example:
```
GRANT ALL PRIVILEGES on db.* to david@'192.58.197.0/255.255.255.0';
```
This will allow everyone to connect from an IP where the following is true:
```
user_ip & netmask = host_ip.
```
In the above example all IP:s in the interval 192.58.197.0 - 192.58.197.255 can connect to the MySQL server.
Wild-card characters are not allowed in the User field, but you can specify a blank value, which matches any name. If the user table entry that matches an incoming connection has a blank user name, the user is considered to be the anonymous user (the user with no name), rather than the name that the client actually specified. This means that a blank user name is used for all further access checking for the duration of the connection (that is, during Stage 2).
The Password field can be blank. This does not mean that any password matches, it means the user must connect without specifying a password.

Non-blank Password values represent encrypted passwords. MySQL does not store passwords in plaintext form for anyone to see. Rather, the password supplied by a user who is attempting to connect is encrypted (using the PASSWORD() function). The encrypted password is then used when the client/server is checking if the password is correct (This is done without the encrypted password ever traveling over the connection.) Note that from MySQL's point of view the encrypted password is the REAL password, so you should not give anyone access to it! In particular, don't give normal users read access to the tables in the mysql database!

The examples below show how various combinations of Host and User values in user table entries apply to incoming connections:

`Host` value	`User` value	Connections matched by entry
`'thomas.loc.gov'`	`'fred'`	`fred`, connecting from `thomas.loc.gov`
`'thomas.loc.gov'`	`''`	Any user, connecting from `thomas.loc.gov`
`'%'`	`'fred'`	`fred`, connecting from any host
`'%'`	`''`	Any user, connecting from any host
`'%.loc.gov'`	`'fred'`	`fred`, connecting from any host in the `loc.gov` domain
`'x.y.%'`	`'fred'`	`fred`, connecting from `x.y.net`, `x.y.com`,`x.y.edu`, etc. (this is probably not useful)
`'144.155.166.177'`	`'fred'`	`fred`, connecting from the host with IP address `144.155.166.177`
`'144.155.166.%'`	`'fred'`	`fred`, connecting from any host in the `144.155.166` class C subnet
`'144.155.166.0/255.255.255.0'`	`'fred'`	Same as previous example

Because you can use IP wild-card values in the Host field (for example, '144.155.166.%' to match every host on a subnet), there is the possibility that someone might try to exploit this capability by naming a host 144.155.166.somewhere.com. To foil such attempts, MySQL disallows matching on hostnames that start with digits and a dot. Thus, if you have a host named something like 1.2.foo.com, its name will never match the Host column of the grant tables. Only an IP number can match an IP wild-card value.

An incoming connection may be matched by more than one entry in the user table. For example, a connection from thomas.loc.gov by fred would be matched by several of the entries just shown above. How does the server choose which entry to use if more than one matches? The server resolves this question by sorting the user table after reading it at startup time, then looking through the entries in sorted order when a user attempts to connect. The first matching entry is the one that is used.

user table sorting works as follows. Suppose the user table looks like this:

+-----------+----------+-
| Host      | User     | ...
+-----------+----------+-
| %         | root     | ...
| %         | jeffrey  | ...
| localhost | root     | ...
| localhost |          | ...
+-----------+----------+-

When the server reads in the table, it orders the entries with the most-specific Host values first ('%' in the Host column means ``any host'' and is least specific). Entries with the same Host value are ordered with the most-specific User values first (a blank User value means ``any user'' and is least specific). The resulting sorted user table looks like this:

+-----------+----------+-
| Host      | User     | ...
+-----------+----------+-
| localhost | root     | ...
| localhost |          | ...
| %         | jeffrey  | ...
| %         | root     | ...
+-----------+----------+-

When a connection is attempted, the server looks through the sorted entries and uses the first match found. For a connection from localhost by jeffrey, the entries with 'localhost' in the Host column match first. Of those, the entry with the blank user name matches both the connecting hostname and user name. (The '%'/'jeffrey' entry would have matched, too, but it is not the first match in the table.)

Here is another example. Suppose the user table looks like this:

+----------------+----------+-
| Host           | User     | ...
+----------------+----------+-
| %              | jeffrey  | ...
| thomas.loc.gov |          | ...
+----------------+----------+-

The sorted table looks like this:

+----------------+----------+-
| Host           | User     | ...
+----------------+----------+-
| thomas.loc.gov |          | ...
| %              | jeffrey  | ...
+----------------+----------+-

A connection from thomas.loc.gov by jeffrey is matched by the first entry, whereas a connection from whitehouse.gov by jeffrey is matched by the second.

A common misconception is to think that for a given user name, all entries that explicitly name that user will be used first when the server attempts to find a match for the connection. This is simply not true. The previous example illustrates this, where a connection from thomas.loc.gov by jeffrey is first matched not by the entry containing 'jeffrey' as the User field value, but by the entry with no user name!

If you have problems connecting to the server, print out the user table and sort it by hand to see where the first match is being made.

6.11 Access Control, Stage 2: Request Verification

Once you establish a connection, the server enters Stage 2. For each request that comes in on the connection, the server checks whether you have sufficient privileges to perform it, based on the type of operation you wish to perform. This is where the privilege fields in the grant tables come into play. These privileges can come from any of the user, db, host, tables_priv, or columns_priv tables. The grant tables are manipulated with GRANT and REVOKE commands. See section 7.35 GRANT and REVOKE Syntax. (You may find it helpful to refer to section 6.9 How the Privilege System Works, which lists the fields present in each of the grant tables.)

The user table grants privileges that are assigned to you on a global basis and that apply no matter what the current database is. For example, if the user table grants you the delete privilege, you can delete rows from any database on the server host! In other words, user table privileges are superuser privileges. It is wise to grant privileges in the user table only to superusers such as server or database administrators. For other users, you should leave the privileges in the user table set to 'N' and grant privileges on a database-specific basis only, using the db and host tables.

The db and host tables grant database-specific privileges. Values in the scope fields may be specified as follows:

The wild-card characters `%' and `_' can be used in the Host and Db fields of either table.
A '%' Host value in the db table means ``any host.'' A blank Host value in the db table means ``consult the host table for further information.''
A '%' or blank Host value in the host table means ``any host.''
A '%' or blank Db value in either table means ``any database.''
A blank User value in either table matches the anonymous user.

The db and host tables are read in and sorted when the server starts up (at the same time that it reads the user table). The db table is sorted on the Host, Db, and User scope fields, and the host table is sorted on the Host and Db scope fields. As with the user table, sorting puts the most-specific values first and least-specific values last, and when the server looks for matching entries, it uses the first match that it finds.

The tables_priv and columns_priv tables grant table- and column-specific privileges. Values in the scope fields may be specified as follows:

The wild-card characters `%' and `_' can be used in the Host field of either table.
A '%' or blank Host value in either table means ``any host.''
The Db, Table_name and Column_name fields cannot contain wild cards or be blank in either table.

The tables_priv and columns_priv tables are sorted on the Host, Db, and User fields. This is similar to db table sorting, although the sorting is simpler because only the Host field may contain wild cards.

The request verification process is described below. (If you are familiar with the access-checking source code, you will notice that the description here differs slightly from the algorithm used in the code. The description is equivalent to what the code actually does; it differs only to make the explanation simpler.)

For administrative requests (shutdown, reload, etc.), the server checks only the user table entry, because that is the only table that specifies administrative privileges. Access is granted if the entry allows the requested operation and denied otherwise. For example, if you want to execute mysqladmin shutdown but your user table entry doesn't grant the shutdown privilege to you, access is denied without even checking the db or host tables. (They contain no Shutdown_priv column, so there is no need to do so.)

For database-related requests (insert, update, etc.), the server first checks the user's global (superuser) privileges by looking in the user table entry. If the entry allows the requested operation, access is granted. If the global privileges in the user table are insufficient, the server determines the user's database-specific privileges by checking the db and host tables:

The server looks in the db table for a match on the Host, Db, and User fields. The Host and User fields are matched to the connecting user's hostname and MySQL user name. The Db field is matched to the database the user wants to access. If there is no entry for the Host and User, access is denied.
If there is a matching db table entry and its Host field is not blank, that entry defines the user's database-specific privileges.
If the matching db table entry's Host field is blank, it signifies that the host table enumerates which hosts should be allowed access to the database. In this case, a further lookup is done in the host table to find a match on the Host and Db fields. If no host table entry matches, access is denied. If there is a match, the user's database-specific privileges are computed as the intersection (not the union!) of the privileges in the db and host table entries, that is, the privileges that are 'Y' in both entries. (This way you can grant general privileges in the db table entry and then selectively restrict them on a host-by-host basis using the host table entries.)

After determining the database-specific privileges granted by the db and host table entries, the server adds them to the global privileges granted by the user table. If the result allows the requested operation, access is granted. Otherwise, the server checks the user's table and column privileges in the tables_priv and columns_priv tables and adds those to the user's privileges. Access is allowed or denied based on the result.

Expressed in boolean terms, the preceding description of how a user's privileges are calculated may be summarized like this:

global privileges
OR (database privileges AND host privileges)
OR table privileges
OR column privileges

It may not be apparent why, if the global user entry privileges are initially found to be insufficient for the requested operation, the server adds those privileges to the database-, table-, and column-specific privileges later. The reason is that a request might require more than one type of privilege. For example, if you execute an INSERT ... SELECT statement, you need both insert and select privileges. Your privileges might be such that the user table entry grants one privilege and the db table entry grants the other. In this case, you have the necessary privileges to perform the request, but the server cannot tell that from either table by itself; the privileges granted by the entries in both tables must be combined.

The host table can be used to maintain a list of secure servers.

At TcX, the host table contains a list of all machines on the local network. These are granted all privileges.

You can also use the host table to indicate hosts that are not secure. Suppose you have a machine public.your.domain that is located in a public area that you do not consider secure. You can allow access to all hosts on your network except that machine by using host table entries like this:

+--------------------+----+-
| Host               | Db | ...
+--------------------+----+-
| public.your.domain | %  | ... (all privileges set to 'N')
| %.your.domain      | %  | ... (all privileges set to 'Y')
+--------------------+----+-

Naturally, you should always test your entries in the grant tables (for example, using mysqlaccess) to make sure your access privileges are actually set up the way you think they are.

6.12 When Privilege Changes Take Effect

When mysqld starts, all grant table contents are read into memory and become effective at that point.

Modifications to the grant tables that you perform using GRANT, REVOKE, or SET PASSWORD are noticed by the server immediately.

If you modify the grant tables manually (using INSERT, UPDATE, etc.), you should execute a FLUSH PRIVILEGES statement or run mysqladmin flush-privileges or mysqladmin reload to tell the server to reload the grant tables. Otherwise your changes will have no effect until you restart the server. If you change the grant tables manually but forget to reload the privileges, you will be wondering why your changes don't seem to make any difference!

When the server notices that the grant tables have been changed, existing client connections are affected as follows:

Table and column privilege changes take effect with the client's next request.
Database privilege changes take effect at the next USE db_name command.

Global privilege changes and password changes take effect the next time the client connects.

6.13 Setting Up the Initial MySQL Privileges

After installing MySQL, you set up the initial access privileges by running scripts/mysql_install_db. See section 4.7.1 Quick Installation Overview. The mysql_install_db script starts up the mysqld server, then initializes the grant tables to contain the following set of privileges:

The MySQL root user is created as a superuser who can do anything. Connections must be made from the local host. NOTE: The initial root password is empty, so anyone can connect as root without a password and be granted all privileges.
An anonymous user is created that can do anything with databases that have a name of 'test' or starting with 'test_'. Connections must be made from the local host. This means any local user can connect without a password and be treated as the anonymous user.
Other privileges are denied. For example, normal users can't use mysqladmin shutdown or mysqladmin processlist.

NOTE: The default privileges are different for Windows. See section 4.13.4 Running MySQL on Windows.

Because your installation is initially wide open, one of the first things you should do is specify a password for the MySQL root user. You can do this as follows (note that you specify the password using the PASSWORD() function):

shell> mysql -u root mysql
mysql> UPDATE user SET Password=PASSWORD('new_password')
           WHERE user='root';
mysql> FLUSH PRIVILEGES;

You can, in MySQL Version 3.22 and above, use the SET PASSWORD statement:

shell> mysql -u root mysql
mysql> SET PASSWORD FOR root=PASSWORD('new_password');

Another way to set the password is by using the mysqladmin command:

shell> mysqladmin -u root password new_password

Only users with write/update access to the mysql database can change the password for others users. All normal users (not anonymous ones) can only change their own password with either of the above commands or with SET PASSWORD=PASSWORD('new password').

Note that if you update the password in the user table directly using the first method, you must tell the server to re-read the grant tables (with FLUSH PRIVILEGES), because the change will go unnoticed otherwise.

Once the root password has been set, thereafter you must supply that password when you connect to the server as root.

You may wish to leave the root password blank so that you don't need to specify it while you perform additional setup or testing. However, be sure to set it before using your installation for any real production work.

See the scripts/mysql_install_db script to see how it sets up the default privileges. You can use this as a basis to see how to add other users.

If you want the initial privileges to be different than those just described above, you can modify mysql_install_db before you run it.

To re-create the grant tables completely, remove all the `.frm', `.MYI', and `.MYD' files in the directory containing the mysql database. (This is the directory named `mysql' under the database directory, which is listed when you run mysqld --help.) Then run the mysql_install_db script, possibly after editing it first to have the privileges you want.

NOTE: For MySQL versions older than Version 3.22.10, you should NOT delete the `.frm' files. If you accidentally do this, you should copy them back from your MySQL distribution before running mysql_install_db.

6.14 Adding New User Privileges to MySQL

You can add users two different ways: by using GRANT statements or by manipulating the MySQL grant tables directly. The preferred method is to use GRANT statements, because they are more concise and less error-prone.

The examples below show how to use the mysql client to set up new users. These examples assume that privileges are set up according to the defaults described in the previous section. This means that to make changes, you must be on the same machine where mysqld is running, you must connect as the MySQL root user, and the root user must have the insert privilege for the mysql database and the reload administrative privilege. Also, if you have changed the root user password, you must specify it for the mysql commands below.

You can add new users by issuing GRANT statements:

shell> mysql --user=root mysql
mysql> GRANT ALL PRIVILEGES ON *.* TO monty@localhost
           IDENTIFIED BY 'some_pass' WITH GRANT OPTION;
mysql> GRANT ALL PRIVILEGES ON *.* TO monty@"%"
           IDENTIFIED BY 'some_pass' WITH GRANT OPTION;
mysql> GRANT RELOAD,PROCESS ON *.* TO admin@localhost;
mysql> GRANT USAGE ON *.* TO dummy@localhost;

These GRANT statements set up three new users:

monty: A full superuser who can connect to the server from anywhere, but who must use a password 'some_pass' to do so. Note that we must issue GRANT statements for both monty@localhost and monty@"%". If we don't add the entry with localhost, the anonymous user entry for localhost that is created by mysql_install_db will take precedence when we connect from the local host, because it has a more specific Host field value and thus comes earlier in the user table sort order.
admin: A user who can connect from localhost without a password and who is granted the reload and process administrative privileges. This allows the user to execute the mysqladmin reload, mysqladmin refresh, and mysqladmin flush-* commands, as well as mysqladmin processlist . No database-related privileges are granted. (They can be granted later by issuing additional GRANT statements.)
dummy: A user who can connect without a password, but only from the local host. The global privileges are all set to 'N' -- the USAGE privilege type allows you to create a user with no privileges. It is assumed that you will grant database-specific privileges later.

You can also add the same user access information directly by issuing INSERT statements and then telling the server to reload the grant tables:

shell> mysql --user=root mysql
mysql> INSERT INTO user VALUES('localhost','monty',PASSWORD('some_pass'),
                'Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y');
mysql> INSERT INTO user VALUES('%','monty',PASSWORD('some_pass'),
                'Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y');
mysql> INSERT INTO user SET Host='localhost',User='admin',
                 Reload_priv='Y', Process_priv='Y';
mysql> INSERT INTO user (Host,User,Password)
                        VALUES('localhost','dummy','');
mysql> FLUSH PRIVILEGES;

Depending on your MySQL version, you may have to use a different number of 'Y' values above (versions prior to Version 3.22.11 had fewer privilege columns). For the admin user, the more readable extended INSERT syntax that is available starting with Version 3.22.11 is used.

Note that to set up a superuser, you need only create a user table entry with the privilege fields set to 'Y'. No db or host table entries are necessary.

The privilege columns in the user table were not set explicitly in the last INSERT statement (for the dummy user), so those columns are assigned the default value of 'N'. This is the same thing that GRANT USAGE does.

The following example adds a user custom who can connect from hosts localhost, server.domain, and whitehouse.gov. He wants to access the bankaccount database only from localhost, the expenses database only from whitehouse.gov, and the customer database from all three hosts. He wants to use the password stupid from all three hosts.

To set up this user's privileges using GRANT statements, run these commands:

shell> mysql --user=root mysql
mysql> GRANT SELECT,INSERT,UPDATE,DELETE,CREATE,DROP
           ON bankaccount.*
           TO custom@localhost
           IDENTIFIED BY 'stupid';
mysql> GRANT SELECT,INSERT,UPDATE,DELETE,CREATE,DROP
           ON expenses.*
           TO custom@whitehouse.gov
           IDENTIFIED BY 'stupid';
mysql> GRANT SELECT,INSERT,UPDATE,DELETE,CREATE,DROP
           ON customer.*
           TO custom@'%'
           IDENTIFIED BY 'stupid';

To set up the user's privileges by modifying the grant tables directly, run these commands (note the FLUSH PRIVILEGES at the end):

shell> mysql --user=root mysql
mysql> INSERT INTO user (Host,User,Password)
       VALUES('localhost','custom',PASSWORD('stupid'));
mysql> INSERT INTO user (Host,User,Password)
       VALUES('server.domain','custom',PASSWORD('stupid'));
mysql> INSERT INTO user (Host,User,Password)
       VALUES('whitehouse.gov','custom',PASSWORD('stupid'));
mysql> INSERT INTO db
       (Host,Db,User,Select_priv,Insert_priv,Update_priv,Delete_priv,
        Create_priv,Drop_priv)
       VALUES
       ('localhost','bankaccount','custom','Y','Y','Y','Y','Y','Y');
mysql> INSERT INTO db
       (Host,Db,User,Select_priv,Insert_priv,Update_priv,Delete_priv,
        Create_priv,Drop_priv)
       VALUES
       ('whitehouse.gov','expenses','custom','Y','Y','Y','Y','Y','Y');
mysql> INSERT INTO db
       (Host,Db,User,Select_priv,Insert_priv,Update_priv,Delete_priv,
        Create_priv,Drop_priv)
       VALUES('%','customer','custom','Y','Y','Y','Y','Y','Y');
mysql> FLUSH PRIVILEGES;

The first three INSERT statements add user table entries that allow user custom to connect from the various hosts with the given password, but grant no permissions to him (all privileges are set to the default value of 'N'). The next three INSERT statements add db table entries that grant privileges to custom for the bankaccount, expenses, and customer databases, but only when accessed from the proper hosts. As usual, when the grant tables are modified directly, the server must be told to reload them (with FLUSH PRIVILEGES) so that the privilege changes take effect.

If you want to give a specific user access from any machine in a given domain, you can issue a GRANT statement like the following:

mysql> GRANT ...
           ON *.*
           TO myusername@"%.mydomainname.com"
           IDENTIFIED BY 'mypassword';

To do the same thing by modifying the grant tables directly, do this:

mysql> INSERT INTO user VALUES ('%.mydomainname.com', 'myusername',
           PASSWORD('mypassword'),...);
mysql> FLUSH PRIVILEGES;

You can also use xmysqladmin, mysql_webadmin, and even xmysql to insert, change, and update values in the grant tables. You can find these utilities in the Contrib directory of the MySQL Website.

6.15 Setting Up Passwords

In most cases you should use GRANT to set up your users/passwords, so the following only applies for advanced users. See section 7.35 GRANT and REVOKE Syntax.

The examples in the preceding sections illustrate an important principle: when you store a non-empty password using INSERT or UPDATE statements, you must use the PASSWORD() function to encrypt it. This is because the user table stores passwords in encrypted form, not as plaintext. If you forget that fact, you are likely to attempt to set passwords like this:

shell> mysql -u root mysql
mysql> INSERT INTO user (Host,User,Password)
       VALUES('%','jeffrey','biscuit');
mysql> FLUSH PRIVILEGES;

The result is that the plaintext value 'biscuit' is stored as the password in the user table. When the user jeffrey attempts to connect to the server using this password, the mysql client encrypts it with PASSWORD() and sends the result to the server. The server compares the value in the user table (the encrypted value of 'biscuit') to the encrypted password (which is not 'biscuit'). The comparison fails and the server rejects the connection:

shell> mysql -u jeffrey -pbiscuit test
Access denied

Passwords must be encrypted when they are inserted in the user table, so the INSERT statement should have been specified like this instead:

mysql> INSERT INTO user (Host,User,Password)
       VALUES('%','jeffrey',PASSWORD('biscuit'));

You must also use the PASSWORD() function when you use SET PASSWORD statements:

mysql> SET PASSWORD FOR jeffrey@"%" = PASSWORD('biscuit');

If you set passwords using the GRANT ... IDENTIFIED BY statement or the mysqladmin password command, the PASSWORD() function is unnecessary. They both take care of encrypting the password for you, so you would specify a password of 'biscuit' like this:

mysql> GRANT USAGE ON *.* TO jeffrey@"%" IDENTIFIED BY 'biscuit';

shell> mysqladmin -u jeffrey password biscuit

NOTE: PASSWORD() does not perform password encryption in the same way that Unix passwords are encrypted. You should not assume that if your Unix password and your MySQL password are the same, that PASSWORD() will result in the same encrypted value as is stored in the Unix password file. See section 6.5 MySQL User Names and Passwords.

6.16 Causes of `Access denied` Errors

If you encounter Access denied errors when you try to connect to the MySQL server, the list below indicates some courses of action you can take to correct the problem:

After installing MySQL, did you run the mysql_install_db script to set up the initial grant table contents? If not, do so. See section 6.13 Setting Up the Initial MySQL Privileges. Test the initial privileges by executing this command:
```
shell> mysql -u root test
```
The server should let you connect without error. You should also make sure you have a file `user.MYD' in the MySQL database directory. Ordinarily, this is `PATH/var/mysql/user.MYD', where PATH is the pathname to the MySQL installation root.
After a fresh installation, you should connect to the server and set up your users and their access permissions:
```
shell> mysql -u root mysql
```
The server should let you connect because the MySQL root user has no password initially. That is also a security risk, so setting the root password is something you should do while you're setting up your other MySQL users. If you try to connect as root and get this error:
```
Access denied for user: '@unknown' to database mysql
```
this means that you don't have an entry in the user table with a User column value of 'root' and that mysqld cannot resolve the hostname for your client. In this case, you must restart the server with the --skip-grant-tables option and edit your `/etc/hosts' or `\windows\hosts' file to add an entry for your host.
If you get an error like the following:
```
shell> mysqladmin -u root -pxxxx ver
Access denied for user: 'root@localhost' (Using password: YES)
```
It means that you are using a wrong password. See section 6.15 Setting Up Passwords. If you have forgot the root password, you can restart mysqld with --skip-grant-tables to change the password. You can find more about this option later on in this manual section. If you get the above error even if you haven't specified a password, this means that you a wrong password in some my.ini file. See section 4.16.5 Option Files. You can avoid using option files with the --no-defaults option, as follows:
```
shell> mysqladmin --no-defaults -u root ver
```
If you updated an existing MySQL installation from a version earlier than Version 3.22.11 to Version 3.22.11 or later, did you run the mysql_fix_privilege_tables script? If not, do so. The structure of the grant tables changed with MySQL Version 3.22.11 when the GRANT statement became functional.
If your privileges seem to have changed in the middle of a session, it may be that a superuser has changed them. Reloading the grant tables affects new client connections, but it also affects existing connections as indicated in section 6.12 When Privilege Changes Take Effect.
If you can't get your password to work, remember that you must use the PASSWORD() function if you set the password with the INSERT, UPDATE, or SET PASSWORD statements. The PASSWORD() function is unnecessary if you specify the password using the GRANT ... INDENTIFIED BY statement or the mysqladmin password command. See section 6.15 Setting Up Passwords.
localhost is a synonym for your local hostname, and is also the default host to which clients try to connect if you specify no host explicitly. However, connections to localhost do not work if you are running on a system that uses MIT-pthreads (localhost connections are made using Unix sockets, which are not supported by MIT-pthreads). To avoid this problem on such systems, you should use the --host option to name the server host explicitly. This will make a TCP/IP connection to the mysqld server. In this case, you must have your real hostname in user table entries on the server host. (This is true even if you are running a client program on the same host as the server.)
If you get an Access denied error when trying to connect to the database with mysql -u user_name db_name, you may have a problem with the user table. Check this by executing mysql -u root mysql and issuing this SQL statement:
```
mysql> SELECT * FROM user;
```
The result should include an entry with the Host and User columns matching your computer's hostname and your MySQL user name.
The Access denied error message will tell you who you are trying to log in as, the host from which you are trying to connect, and whether or not you were using a password. Normally, you should have one entry in the user table that exactly matches the hostname and user name that were given in the error message. For example if you get an error message that contains Using password: NO, this means that you tried to login without an password.
If you get the following error when you try to connect from a different host than the one on which the MySQL server is running, then there is no row in the user table that matches that host:
```
Host ... is not allowed to connect to this MySQL server
```
You can fix this by using the command-line tool mysql (on the server host!) to add a row to the user, db, or host table for the user/hostname combination from which you are trying to connect and then execute mysqladmin flush-privileges. If you are not running MySQL Version 3.22 and you don't know the IP number or hostname of the machine from which you are connecting, you should put an entry with '%' as the Host column value in the user table and restart mysqld with the --log option on the server machine. After trying to connect from the client machine, the information in the MySQL log will indicate how you really did connect. (Then replace the '%' in the user table entry with the actual hostname that shows up in the log. Otherwise, you'll have a system that is insecure.) Another reason for this error on Linux is that you are using a binary MySQL version that is compiled with a different glibc version than the one you are using. In this case you should either upgrade your OS/glibc or download

Available	Barnes and Noble
Publisher	New Riders
Author	Paul DuBois
Pub Date	1st Edition December 1999
ISBN	0735709211
Pages	800
Price	$49.99 US
Downloadable examples	`samp_db.tar.gz`
Errata	are available here

`mysql`	Compiled on native Windows, which offers very limited text editing capabilities.
`mysqlc`	Compiled with the Cygnus GNU compiler and libraries, which offers `readline` editing.

Filename	Purpose
`/etc/my.cnf`	Global options
`DATADIR/my.cnf`	Server-specific options
`defaults-extra-file`	The file specified with --defaults-extra-file=#
`~/.my.cnf`	User-specific options