MySQL Reference Manual for version 3.23.58.
The MySQL (R) software delivers a very fast, multi-threaded,
multi-user, and robust SQL (Structured Query Language)
database server.
MySQL Server is intended for mission-critical, heavy-load
production systems as well as for embedding into mass-deployed software.
MySQL is a trademark of MySQL AB.
The MySQL software is Dual Licensed. Users can choose to
use the MySQL software as an Open Source/Free Software
product under the terms of the GNU General Public License
(http://www.gnu.org/licenses/) or can purchase a standard
commercial license from MySQL AB.
See section 1.4 MySQL Support and Licensing.
The MySQL web site (http://www.mysql.com/) provides the
latest information about the MySQL software.
The following list describes some sections of particular interest in this manual:
-
For information about the company behind the
MySQL Database Server,
see section 1.3 What Is MySQL AB?.
-
For a discussion about the capabilities of the
MySQL Database Server,
see section 1.2.2 The Main Features of MySQL.
-
For installation instructions, see section 2 Installing MySQL.
-
For tips on porting the
MySQL Database Software to new architectures
or operating systems, see section E Porting to Other Systems.
-
For information about upgrading from a Version 4.0 release, see
section 2.5.1 Upgrading From Version 4.0 to 4.1.
-
For information about upgrading from a Version 3.23 release, see
section 2.5.2 Upgrading From Version 3.23 to 4.0.
-
For information about upgrading from a Version 3.22 release, see
section 2.5.3 Upgrading From Version 3.22 to 3.23.
-
For a tutorial introduction to the
MySQL Database Server,
see section 3 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 D MySQL Change History.
-
For a list of currently known bugs and misfeatures, see section 1.7.6 Known Errors and Design Deficiencies in MySQL.
-
For future plans, see section 1.8 MySQL and The Future (The TODO).
-
For a list of all the contributors to this project, see section C Credits.
Important:
Reports of errors (often called bugs), as well as questions and comments,
should be sent to the general MySQL mailing list.
See section 1.6.1.1 The MySQL Mailing Lists.
See section 1.6.1.3 How to Report Bugs or Problems.
The mysqlbug script should be used to generate bug reports on Unix.
(Windows distributions contain a file `mysqlbug.txt' in the base
directory that can be used as a template for a bug report.)
For source distributions, the mysqlbug script can be found in the
`scripts' directory. For binary distributions, mysqlbug
can be found in the `bin' directory (`/usr/bin' for the
MySQL-server RPM package).
If you have found a sensitive security bug in MySQL Server,
you should send an e-mail to security@mysql.com.
This is the MySQL reference manual; it documents MySQL
up to Version 3.23.58. Functional changes are always
indicated with reference to the version, so this manual is also suitable
if you are using an older version of the MySQL software
(such as 3.23 or 4.0-production).
There are also references for version 5.0 (development).
Being a reference manual, it does not provide general instruction on
SQL or relational database concepts.
As the MySQL Database Software is under constant development,
the manual is also updated frequently.
The most recent version of this manual is available at
http://www.mysql.com/documentation/ in many different formats,
including HTML, PDF, and Windows HLP 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.
If you have a hard time finding information in the manual, you can try
our searchable version at http://www.mysql.com/doc/.
If you have any suggestions concerning additions or corrections to this
manual, please send them to the documentation team at docs@mysql.com.
This manual was initially written by David Axmark and Michael (Monty)
Widenius. It is now maintained by the MySQL Documentation Team,
consisting of Arjen Lentz, Paul DuBois and Stefan Hinz.
For the many other contributors, see section C Credits.
The copyright (2003) to this manual is owned by the Swedish company
MySQL AB. See section 1.4.2 Copyrights and Licenses Used by MySQL.
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 wildcard, use the `%'
character.''
- italic
-
Italic font is used for emphasis, like this.
- boldface
-
Boldface font is used in table headings and 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
Database, table, and column names must often 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 keywords are not case-sensitive and may be written in uppercase or
lowercase. This manual uses uppercase.
In syntax descriptions, square brackets (`[' and `]') are used
to indicate optional words or clauses. For example, in the following
statement, IF EXISTS is optional:
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}
MySQL, the most popular Open Source SQL database, is
developed, distributed, and supported by MySQL AB. MySQL AB is a
commercial company, founded by the MySQL developers, that builds its business
providing services around the MySQL database.
See section 1.3 What Is MySQL AB?.
The MySQL web site (http://www.mysql.com/)
provides the latest information about MySQL software and
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 Server. Since computers are very good at handling large
amounts of data, database management systems play 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
SQL part of ``MySQL'' stands for ``Structured
Query Language''. SQL is the most common standardised language used to
access databases and is defined by the ANSI/ISO SQL Standard.(The SQL
standard has been evolving since 1986 and several versions exist. In this
manual, ''SQL-92'' refers to the standard released in 1992,
''SQL-99'' refers to the standard released in 1999, and
''SQL:2003'' refers to the version of the standard that is expected
to be released in mid-2003.We use the term ''the SQL standard'' to
mean the current version of the SQL Standard at any time.)
- MySQL software is
Open Source.
-
Open Source means that it is possible for anyone to use and modify the software.
Anybody can download the MySQL software from the Internet and use it
without paying anything. If you wish, you may study the source code
and change it to suit your needs. The MySQL software uses the
GPL (GNU General Public License),
http://www.gnu.org/licenses/, 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 code into a commercial application you can buy a
commercially licensed version from us.
See section 1.4.3 MySQL Licenses.
- Why use the MySQL Database Server?
-
The
MySQL Database Server is very fast, reliable, and easy to use.
If that is what you are looking for, you should give it a try.
MySQL Server also has a practical set of features developed in
close cooperation with our users. You can find a performance comparison
of MySQL Server with other database managers on our benchmark page.
See section 5.1.4 The MySQL Benchmark Suite.
MySQL Server was originally developed to handle 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 Server today offers a rich and
useful set of functions. Its connectivity, speed, and security make
MySQL Server highly suited for accessing databases on the Internet.
- The technical features of MySQL Server
-
For advanced technical information, see section 6 MySQL Language Reference.
The
MySQL Database Software 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 a wide range of programming interfaces (APIs).
We also provide MySQL Server as a multi-threaded library which you
can link into your application to get a smaller, faster, easier-to-manage
product.
- There is a large amount of contributed MySQL software available.
-
It is very likely that you will find that your favorite application or
language already supports the
MySQL Database Server.
The official way to pronounce MySQL is ``My Ess Que Ell'' (not
``my sequel''), but we don't mind if you pronounce it as ``my sequel''
or in some other localised way.
We 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 clear. Our base
directory and a large number of our libraries and tools have had the prefix
``my'' for well over 10 years. However, co-founder Monty Widenius'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.
The name of the MySQL Dolphin (our logo) is Sakila. Sakila was chosen
by the founders of MySQL AB from a huge list of names suggested by users
in our "Name the Dolphin" contest. The winning name was submitted by
Ambrose Twebaze, an open source software developer from Swaziland, Africa.
According to Ambrose, the name Sakila has its roots in SiSwati, the local
language of Swaziland. Sakila is also the name of a town in Arusha,
Tanzania, near Ambrose's country of origin, Uganda.
The following list describes some of the important characteristics
of the MySQL Database Software. See section 1.5.1 MySQL 4.0 in a Nutshell.
- Internals and Portability
-
-
Written in C and C++. Tested with a broad range of different compilers.
-
Works on many different platforms. See section 2.2.5 Operating Systems Supported by MySQL.
-
Uses GNU Automake, Autoconf, and Libtool for portability.
-
APIs for C, C++, Eiffel, Java, Perl, PHP, Python, Ruby, and Tcl.
See section 9 MySQL APIs.
-
Fully multi-threaded using kernel threads. This means it can easily
use multiple CPUs if available.
-
Transactional and non-transactional storage engines.
-
Very fast B-tree disk tables (MyISAM) with index compression.
-
Relatively easy to add another storage engine. This is useful if you
want to add an SQL interface to an in-house database.
-
A very fast thread-based memory allocation system.
-
Very fast joins using an optimised one-sweep multi-join.
-
In-memory hash tables which are used as temporary tables.
-
SQL functions are implemented through a highly optimised class library and
should be as fast as possible. Usually there isn't any memory allocation
at all after query initialisation.
-
The
MySQL code gets tested with Purify
(a commercial memory leakage detector) as well as with Valgrind,
a GPL tool (http://developer.kde.org/~sewardj/).
-
Available as client/server or embedded (linked) version.
- Column Types
-
-
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 6.2 Column Types.
-
Fixed-length and variable-length records.
- Commands and Functions
-
- Security
-
-
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.
- Scalability and Limits
-
-
Handles large databases. We use
MySQL Server with databases that
contain 50 million records. We also know of users that
use MySQL Server with 60,000 tables and about 5,000,000,000 rows.
-
Up to 32 indexes per table are allowed. Each index may consist of 1 to 16
columns or parts of columns. The maximum index width is 500 bytes
(this may be changed when compiling
MySQL Server).
An index may use a prefix of a CHAR or VARCHAR field.
- Connectivity
-
-
Clients may connect to the
MySQL server using TCP/IP Sockets,
Unix Sockets (Unix), or Named Pipes (NT).
-
ODBC (Open-DataBase-Connectivity) support for Win32 (with source).
All ODBC 2.5 functions are supported, as are many others. For example, you can use
MS Access to connect to your
MySQL server. See section 9.2 MySQL ODBC Support.
- Localisation
-
-
The server can provide error messages to clients in many languages.
See section 4.6.2 Non-English Error Messages.
-
Full support for several different character sets, including
ISO-8859-1 (Latin1), german, big5, ujis, and more. For example,
the Scandinavian characters `@^a', `@"a' and `@"o' are
allowed in table and column names.
-
All data is 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. To see an example of very advanced sorting, look
at the Czech sorting code. MySQL Server supports many different
character sets that can be specified at compile and runtime.
- Clients and Tools
-
-
Includes
myisamchk, a very fast utility for table checking,
optimisation, and repair. All of the functionality of myisamchk
is also available through the SQL interface.
See section 4 Database Administration.
-
All
MySQL programs can be invoked with the --help or -?
options to obtain online assistance.
This section addresses the questions ``How stable is MySQL Server?''
and ``Can I depend on MySQL Server in this project?''
We will try to clarify these issues and answer some important
questions that concern many potential users. The information in this
section is based on data gathered from the mailing list, which is
very active in identifying problems as well as reporting types of use.
Original code stems back from the early '80s, providing a stable code
base, and the ISAM table format remains backward-compatible.
At TcX, the predecessor of MySQL AB, MySQL code has worked
in projects since mid-1996, without any problems.
When the MySQL Database Software was released to a wider public,
our new users quickly found some pieces of ``untested code''. Each new release
since then has had fewer portability problems (even though each new release
has also had many new features).
Each release of the MySQL Server has been usable. Problems have occurred
only when users try code from the ``gray zones.'' Naturally, new users
don't know what the gray zones are; this section therefore attempts to
document those areas that are currently known.
The descriptions mostly deal with Version 3.23 and 4.0 of MySQL Server.
All known and reported bugs are fixed in the latest version, with the
exception of those listed in the bugs section, which are things that
are design-related. See section 1.7.6 Known Errors and Design Deficiencies in MySQL.
The MySQL Server design is multi-layered with independent modules.
Some of the newer modules are listed here with an indication of how
well-tested each of them is:
- Replication -- Gamma
-
Large server clusters using replication are in production use, with
good results. Work on enhanced replication features is continuing
in
MySQL 4.x.
InnoDB tables -- Stable (in 3.23 from 3.23.49)
-
The
InnoDB transactional storage engine has been declared
stable in the MySQL 3.23 tree, starting from version 3.23.49.
InnoDB is being used in large, heavy-load production systems.
BDB tables -- Gamma
-
The
Berkeley DB code is very stable, but we are still improving
the BDB transactional storage engine interface in
MySQL Server, so it will take some time before this is as well
tested as the other table types.
FULLTEXT -- Beta
-
Full-text search works but is not yet widely used.
Important enhancements have been implemented in
MySQL 4.0.
MyODBC 3.51 (uses ODBC SDK 3.51) -- Stable
-
In wide production use. Some issues brought up appear to be
application-related and independent of the ODBC driver or underlying
database server.
- Automatic recovery of
MyISAM tables -- Gamma
-
This status applies only to the new code in the
MyISAM storage
engine that checks if the table was closed properly on open and
executes an automatic check/repair of the table if it wasn't.
- Bulk-insert -- Alpha
-
New feature in
MyISAM tables in MySQL 4.0 for faster
insert of many rows.
- 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 mysqld with the --skip-external-locking flag.
Problems are known to occur on some Linux systems, and on SunOS when
using NFS-mounted filesystems.
MySQL AB provides high-quality support for paying customers,
and 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.
MySQL Version 3.22 had a 4 GB (4 gigabyte) limit on table size. With the
MyISAM table type in MySQL Version 3.23, the maximum table
size was pushed up to 8 million terabytes (2 ^ 63 bytes).
In effect, then, the table size for MySQL databases is normally
limited by the operating system.
Note, however, that operating systems have their own file-size
limits. Here are some examples:
| Operating System | File-Size Limit
|
| Linux-Intel 32 bit | 2 GB, much more when using LFS
|
| Linux-Alpha | 8 TB (?)
|
| Solaris 2.5.1 | 2 GB (possible 4GB with patch)
|
| Solaris 2.6 | 4 GB (can be changed with flag)
|
| Solaris 2.7 Intel | 4 GB
|
| Solaris 2.7 UltraSPARC | 512 GB
|
On Linux 2.2 you can get tables larger than 2 GB in size by using the LFS
patch for the ext2 filesystem. On Linux 2.4 patches also exist for ReiserFS
to get support for big files. Most current distributions are based on
kernel 2.4 and already include all the required Large File Support (LFS)
patches. However, the maximum available file size still depends on several
factors, one of them being the file system used to store MySQL tables.
For a very detailed overview about LFS in Linux, have a look at Andreas
Jaeger's "Large File Support in Linux" page at
http://www.suse.de/~aj/linux_lfs.html.
By default, MySQL tables have a maximum size of about 4 GB. You can
check the maximum table size for a table with the SHOW TABLE STATUS
command or with the myisamchk -dv table_name.
See section 4.5.7 SHOW Syntax.
If you need a table that will be larger than 4 GB in size (and your
operating system supports it), set the AVG_ROW_LENGTH and
MAX_ROWS parameters accordingly when you create your table.
See section 6.5.3 CREATE TABLE Syntax. You can also set these parameters later, with
ALTER TABLE. See section 6.5.4 ALTER TABLE Syntax.
If your big table is a read-only table, you could use
myisampack to merge and compress many tables into one.
myisampack usually compresses a table by at least 50%, so you can
have, in effect, much bigger tables. See section 4.7.4 myisampack, The MySQL Compressed Read-only Table Generator.
You can get around the operating system file limit for MyISAM
datafiles using the RAID option. See section 6.5.3 CREATE TABLE Syntax.
Another solution can be the included MERGE library, which allows
you to handle a collection of identical tables as one.
See section 7.2 MERGE Tables.
The MySQL Server itself has no problems with Year 2000 (Y2K)
compliance:
-
MySQL Server uses Unix time functions and has no problems with dates
until 2069. All 2-digit years are considered to be in the range
1970 to 2069, which means that if you store 01 in a
YEAR column, MySQL Server treats it as 2001.
-
All
MySQL date functions are stored in one file, `sql/time.cc',
and are coded very carefully to be year 2000-safe.
-
In
MySQL Version 3.22 and later, the YEAR column type
can store years 0 and 1901 to 2155 in one byte and
display them using two or four digits.
You may run into problems with applications that use MySQL Server
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 Server
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 example shows that the DATE and DATETIME datatypes will not
give any problems with future dates (they handle dates until the year
9999).
The TIMESTAMP datatype, which is used to store the current time, supports
values that range from 19700101000000 to 20300101000000 on 32-bit
machines (signed value). On 64-bit machines, TIMESTAMP handles values
up to 2106 (unsigned value).
Even though MySQL Server is Y2K-compliant, it is your responsibility
to provide unambiguous input. See section 6.2.2.1 Y2K Issues and Date Types for MySQL Server's
rules for dealing with ambiguous date input data (data containing 2-digit
year values).
MySQL AB is the company of the MySQL founders and main
developers. MySQL AB was originally established in Sweden by
David Axmark, Allan Larsson, and Michael Monty Widenius.
The developers of the MySQL server are all employed by the company.
We are a virtual organisation with people in a dozen countries around
the world. We communicate extensively over the Net every day with one another
and with our users, supporters, and partners.
We are dedicated to developing the MySQL software and spreading
our database to new users. MySQL AB owns the copyright to the
MySQL source code, the MySQL logo and trademark, and this
manual. See section 1.2 What Is MySQL?.
The MySQL core values show our dedication to MySQL and
Open Source.
We want the MySQL Database Software to be:
-
The best and the most widely used database in the world.
-
Available to, and affordable by all.
-
Easy to use.
-
Continuously improving while remaining fast and safe.
-
Fun to use and improve.
-
Free from bugs.
MySQL AB and the people at 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 e-mail and provide support.
-
Are a virtual company, networking with others.
-
Work against software patents.
The MySQL web site (http://www.mysql.com/)
provides the latest information about MySQL and MySQL AB.
By the way, the ``AB'' part of the company name is the
acronym for the Swedish ``aktiebolag'', or ``stock company.''
It translates to ``MySQL, Inc.'' In fact, MySQL Inc. and MySQL GmbH
are examples of MySQL AB subsidiaries. They are located in the US and Germany,
respectively.
One of the most common questions we encounter is:
``How can you make a living from something you give away for free?''
This is how.
MySQL AB makes money on support, services, commercial licenses,
and royalties. We use these revenues to fund product development
and to expand the MySQL business.
The company has been profitable since its inception. In October 2001,
we accepted venture financing from leading Scandinavian investors and
a handful of business angels. This investment is used to solidify our
business model and build a basis for sustainable growth.
MySQL AB is run and owned by the founders and main developers of
the MySQL database. The developers are committed to giving support
to customers and other users in order to stay in touch with their needs
and problems. All our support is given by qualified developers. Really
tricky questions are answered by Michael Monty Widenius, principal
author of the MySQL Server.
See section 1.4.1 Support Offered by MySQL AB.
For more information and ordering support at various levels, see
http://www.mysql.com/support/ or contact our sales staff at
sales@mysql.com.
MySQL AB delivers MySQL and related training worldwide.
We offer both open courses and in-house courses tailored to the
specific needs of your company. MySQL Training is also available
through our partners, the Authorised MySQL Training Centers.
Our training material uses the same example databases used in our
documentation and our sample applications, and is always updated
to reflect the latest MySQL version. Our trainers are backed by
the development team to guarantee the quality of the training and the
continuous development of the course material. This also ensures
that no questions raised during the courses remain unanswered.
Attending our training courses will enable you to achieve your MySQL
application goals. You will also:
-
Save time.
-
Improve the performance of your application(s).
-
Reduce or eliminate the need for additional hardware, decreasing cost.
-
Enhance security.
-
Increase customers' and co-workers' satisfaction.
-
Prepare yourself for
MySQL Certification.
If you are interested in our training as a potential participant or
as a training partner, please visit the training section at
http://www.mysql.com/training/ or contact us at:
training@mysql.com.
For details about the MySQL Certification Program, please see
http://www.mysql.com/certification/.
MySQL AB and its Authorised Partners offer consulting
services to users of MySQL Server and to those who embed
MySQL Server in their own software, all over the world.
Our consultants can help you design and tune your databases, construct
efficient queries, tune your platform for optimal performance, resolve
migration issues, set up replication, build robust transactional
applications, and more.
We also help customers embed MySQL Server in their products and
applications for large-scale deployment.
Our consultants work in close collaboration with our development team,
which ensures the technical quality of our professional services.
Consulting assignments range from 2-day power-start sessions to
projects that span weeks and months. Our expertise not only covers
MySQL Server---it also extends into programming and scripting
languages such as PHP, Perl, and more.
If you are interested in our consulting services or want to become a
consulting partner, please visit the consulting section of our web site
at http://www.mysql.com/consulting/ or contact our consulting
staff at consulting@mysql.com.
The MySQL database is released under the
GNU General Public License (GPL).
This means that the MySQL software can be used free of charge
under the GPL. If you do not want to be bound by the GPL
terms (such as the requirement that your application must also be GPL,
you may purchase a commercial license for the same product
from MySQL AB; see http://www.mysql.com/products/pricing.html.
Since MySQL AB owns the copyright to the MySQL source code,
we are able to employ Dual Licensing, which means that the same
product is available under GPL and under a commercial
license. This does not in any way affect the Open Source
commitment of MySQL AB. For details about when a commercial
license is required, please see section 1.4.3 MySQL Licenses.
We also sell commercial licenses of third-party Open Source GPL
software that adds value to MySQL Server. A good example is the
InnoDB transactional storage engine that offers ACID
support, row-level locking, crash recovery, multi-versioning, foreign
key support, and more. See section 7.5 InnoDB Tables.
MySQL AB has a worldwide partner programme that covers training
courses, consulting and support, publications, plus reselling and
distributing MySQL and related products. MySQL AB Partners
get visibility on the http://www.mysql.com/ web site and the right
to use special versions of the MySQL trademarks to identify their
products and promote their business.
If you are interested in becoming a MySQL AB Partner, please e-mail
partner@mysql.com.
The word MySQL and the MySQL dolphin logo are trademarks of
MySQL AB. See section 1.4.4 MySQL AB Logos and Trademarks.
These trademarks represent a significant value that the MySQL
founders have built over the years.
The MySQL web site (http://www.mysql.com/) is popular among
developers and users. In October 2001, we served 10 million page views.
Our visitors represent a group that makes purchase decisions and
recommendations for both software and hardware. Twelve percent of our
visitors authorise purchase decisions, and only nine percent are not
involved in purchase decisions at all. More than 65% have made one or
more online business purchases within the last half-year, and 70% plan
to make one in the next few months.
The MySQL web site (http://www.mysql.com/)
provides the latest information about MySQL and MySQL AB.
For press services and inquiries not covered in our News releases
(http://www.mysql.com/news/), please send an e-mail to
press@mysql.com.
If you have a valid support contract with MySQL AB, you will
get timely, precise answers to your technical questions about the
MySQL software. For more information, see section 1.4.1 Support Offered by MySQL AB.
On our web site, see http://www.mysql.com/support/, or send
an e-mail to sales@mysql.com.
For information about MySQL training, please visit the training
section at http://www.mysql.com/training/. If you have
restricted access to the Internet, please contact the MySQL AB
training staff via e-mail at training@mysql.com.
See section 1.3.1.2 Training and Certification.
For information on the MySQL Certification Program, please see
http://www.mysql.com/certification/.
See section 1.3.1.2 Training and Certification.
If you're interested in consulting, please visit the consulting
section of our web site at http://www.mysql.com/consulting/. If you have
restricted access to the Internet, please contact the MySQL AB
consulting staff via e-mail at consulting@mysql.com.
See section 1.3.1.3 Consulting.
Commercial licenses may be purchased online at
https://order.mysql.com/. There you will also find information
on how to fax your purchase order to MySQL AB. More information
about licensing can be found at
http://www.mysql.com/products/pricing.html.
If you have
questions regarding licensing or you want a quote for a high-volume
license deal, please fill in the contact form on our web site
(http://www.mysql.com/) or send an e-mail message
to licensing@mysql.com (for licensing questions) or to
sales@mysql.com (for sales inquiries).
See section 1.4.3 MySQL Licenses.
If you represent a business that is interested in partnering with
MySQL AB, please send an e-mail to partner@mysql.com.
See section 1.3.1.5 Partnering.
For more information on the MySQL trademark policy, refer to
http://www.mysql.com/company/trademark.html or send an e-mail to
trademark@mysql.com.
See section 1.4.4 MySQL AB Logos and Trademarks.
If you are interested in any of the MySQL AB jobs listed in our
jobs section (http://www.mysql.com/company/jobs/),
please send an e-mail to jobs@mysql.com.
Please do not send your CV as an attachment, but rather as plain text
at the end of your e-mail message.
For general discussion among our many users, please direct your
attention to the appropriate mailing list.
See section 1.6.1 MySQL Mailing Lists.
Reports of errors (often called bugs), as well as questions and
comments, should be sent to the general MySQL mailing list.
See section 1.6.1.1 The MySQL Mailing Lists.
If you have found a sensitive
security bug in the MySQL Server, please send an e-mail
to security@mysql.com.
See section 1.6.1.3 How to Report Bugs or Problems.
If you have benchmark results that we can publish, please
contact us via e-mail at benchmarks@mysql.com.
If you have suggestions concerning additions or corrections to this
manual, please send them to the manual team via e-mail at docs@mysql.com.
For questions or comments about the workings or content of the
MySQL web site (http://www.mysql.com/),
please send an e-mail to webmaster@mysql.com.
MySQL AB has a privacy policy, which can be read at
http://www.mysql.com/company/privacy.html.
For any queries regarding this policy, please send an e-mail to
privacy@mysql.com.
For all other inquires, please send an e-mail to info@mysql.com.
This section describes MySQL support and licensing arrangements.
Technical support from MySQL AB means individualised answers
to your unique problems direct from the software engineers who code
the MySQL database engine.
We try to take a broad and inclusive view of technical support. Almost
any problem involving MySQL software is important to us if it's
important to you.
Typically customers seek help on how to get different commands and
utilities to work, remove performance bottlenecks, restore crashed
systems, understand operating system or networking impacts on MySQL,
set up best practices for backup and recovery, utilise APIs, and so on.
Our support covers only the MySQL server and our own utilities,
not third-party products that access the MySQL server, though we
try to help with these where we can.
Detailed information about our various support options is given at
http://www.mysql.com/support/, where support contracts can also be
ordered online. If you have restricted access to the Internet, please contact
our sales staff via e-mail at sales@mysql.com.
Technical support is like life insurance. You can live happily
without it for years, but when your hour arrives it becomes
critically important, yet it's too late to buy it.
If you use MySQL Server for important applications and encounter
sudden difficulties, it may be too time consuming to figure out all the answers
yourself. You may need immediate access to the most experienced
MySQL troubleshooters available, those employed by MySQL AB.
MySQL AB owns the copyright to the MySQL source code,
the MySQL logos and trademarks and this manual.
See section 1.3 What Is MySQL AB?.
Several different licenses are relevant to the MySQL
distribution:
-
All the
MySQL-specific source in the server, the mysqlclient
library and the client, as well as the GNU readline library
is covered by the GNU General Public License.
See section H GNU General Public License.
The text of this license can be found as the file `COPYING'
in the distribution.
-
The
GNU getopt library is covered by the
GNU Lesser General Public License.
See section I GNU Lesser General Public License.
-
Some parts of the source (the
regexp library) are covered
by a Berkeley-style copyright.
-
Older versions of
MySQL (3.22 and earlier) are subject to a
stricter license
(http://www.mysql.com/products/mypl.html).
See the documentation of the specific version for information.
-
The
MySQL reference manual is currently not distributed
under a GPL-style license. Use of the manual is subject to the
following terms:
-
Conversion to other formats is allowed, but the actual content
may not be altered or edited in any way.
-
You may create a printed copy for your own personal use.
-
For all other uses, such as selling printed copies or using
(parts of) the manual in another publication, prior written
agreement from
MySQL AB is required.
Please send an e-mail to docs@mysql.com for more information or
if you are interested in doing a translation.
For information about how the MySQL licenses work in practice,
please refer to section 1.4.3 MySQL Licenses.
Also see section 1.4.4 MySQL AB Logos and Trademarks.
The MySQL software is released under the
GNU General Public License (GPL),
which is probably the best known Open Source license.
The formal terms of the GPL license can be found at
http://www.gnu.org/licenses/.
See also http://www.gnu.org/licenses/gpl-faq.html and
http://www.gnu.org/philosophy/enforcing-gpl.html.
Since the MySQL software is released under the GPL,
it may often be used for free, but for certain uses you may want
or need to buy commercial licenses from MySQL AB at
https://order.mysql.com/.
See http://www.mysql.com/products/licensing.html for
more information.
Older versions of MySQL (3.22 and earlier) are subject to a
stricter license
(http://www.mysql.com/products/mypl.html).
See the documentation of the specific version for information.
Please note that the use of the MySQL software under commercial
license, GPL, or the old MySQL license does not
automatically give you the right to use MySQL AB trademarks.
See section 1.4.4 MySQL AB Logos and Trademarks.
The GPL license is contagious in the sense that when a program
is linked to a GPL program all the source code for all the parts
of the resulting product must also be released under the GPL.
If you do not follow this GPL requirement, you break the license
terms and forfeit your right to use the GPL program altogether.
You also risk damages.
You need a commercial license:
-
When you link a program with any
GPL code from the MySQL
software and don't want the resulting product to be licensed under GPL,
perhaps because you want to build a commercial product or keep the added
non-GPL code closed source for other reasons. When purchasing
commercial licenses, you are not using the MySQL software under
GPL even though it's the same code.
-
When you distribute a non-
GPL application that only works with the
MySQL software and ship it with the MySQL software. This type
of solution is considered to be linking even if it's done over a network.
-
When you distribute copies of the
MySQL software without providing
the source code as required under the GPL license.
-
When you want to support the further development of the
MySQL
database even if you don't formally need a commercial license.
Purchasing support directly from MySQL AB is another good way
of contributing to the development of the MySQL software, with
immediate advantages for you.
See section 1.4.1 Support Offered by MySQL AB.
If you require a license, you will need one for each installation of the
MySQL software. This covers any number of CPUs on a machine, and there
is no artificial limit on the number of clients that connect to the server
in any way.
For commercial licenses, please visit our website at
http://www.mysql.com/products/licensing.html.
For support contracts, see http://www.mysql.com/support/.
If you have special needs or you have restricted access to the Internet,
please contact our sales staff via e-mail at sales@mysql.com.
You can use the MySQL software for free under the GPL if
you adhere to the conditions of the GPL.
For additional details, including answers to common questions about the GPL,
see the generic FAQ from the Free Software Foundation at
http://www.gnu.org/licenses/gpl-faq.html.
Common uses of the GPL include:
-
When you distribute both your own application and the
MySQL
source code under the GPL with your product.
-
When you distribute the
MySQL source code bundled with other
programs that are not linked to or dependent on the MySQL system
for their functionality even if you sell the distribution commercially.
This is called mere aggregation in the GPL license.
-
When you are not distributing any part of the
MySQL
system, you can use it for free.
-
When you are an Internet Service Provider (ISP), offering web hosting
with
MySQL servers for your customers.
We encourage people to use ISPs that have MySQL support,
as this will give them the confidence that their ISP will, in fact,
have the resources to solve any problems they may experience with
the MySQL installation. Even if an ISP does not have
a commercial license for MySQL Server, their customers
should at least be given read access to the source of the MySQL
installation so that the customers can verify that it is correctly patched.
-
When you use the
MySQL database software in conjunction with a
web server, you do not need a commercial license (so long as it is not
a product you distribute). This is true even if you run a commercial
web server that uses MySQL Server, because you are not
distributing any part of the MySQL system. However, in this
case we would like you to purchase MySQL support because the
MySQL software is helping your enterprise.
If your use of MySQL database software does not require a commercial
license, we encourage you to purchase support from MySQL AB anyway.
This way you contribute toward MySQL development and also gain
immediate advantages for yourself. See section 1.4.1 Support Offered by MySQL AB.
If you use the MySQL database software in a commercial context
such that you profit by its use, we ask that you further the development
of the MySQL software by purchasing some level of support. We feel
that if the MySQL database helps your business, it is reasonable to
ask that you help MySQL AB.
(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.)
Many users of the MySQL database want to display the
MySQL AB dolphin logo on their web sites, books, or
boxed products. We welcome and encourage this, although it should be
noted that the word MySQL and the MySQL dolphin logo
are trademarks of MySQL AB and may only be used as stated in
our trademark policy at
http://www.mysql.com/company/trademark.html.
The MySQL dolphin logo was designed by the Finnish advertising
agency Priority in 2001. The dolphin was chosen as a suitable symbol
for the MySQL database since it is a smart, fast, and lean animal,
effortlessly navigating oceans of data. We also happen to like dolphins.
The original MySQL logo may only be used by representatives of
MySQL AB and by those having a written agreement allowing them
to do so.
We have designed a set of special Conditional Use logos that may be
downloaded from our web site at
http://www.mysql.com/press/logos.html
and used on third-party web sites without written permission from
MySQL AB.
The use of these logos is not entirely unrestricted but, as the name
implies, subject to our trademark policy that is also available on our
web site. You should read through the trademark policy if you plan to
use them. The requirements are basically as follows:
-
Use the logo you need as displayed on the http://www.mysql.com/
site. You may scale it to fit your needs, but may not change colours or design,
or alter the graphics in any way.
-
Make it evident that you, and not
MySQL AB, are the creator and
owner of the site that displays the MySQL trademark.
-
Don't use the trademark in a way that is detrimental to
MySQL AB
or to the value of MySQL AB trademarks. We reserve the right to
revoke the right to use the MySQL AB trademark.
-
If you use the trademark on a web site, make it clickable, leading directly
to http://www.mysql.com/.
-
If you are use the
MySQL database under GPL in an
application, your application must be Open Source and must
be able to connect to a MySQL server.
Contact us via e-mail at trademark@mysql.com to inquire about special
arrangements to fit your needs.
You need written permission from MySQL AB before using MySQL
logos in the following cases:
-
When displaying any
MySQL AB logo anywhere except on your web site.
-
When displaying any
MySQL AB logo except the Conditional Use
logos mentioned previously on web sites or elsewhere.
Due to legal and commercial reasons we monitor the use of MySQL
trademarks on products, books, and other items. We usually require a fee for
displaying MySQL AB logos on commercial products, since we think
it is reasonable that some of the revenue is returned to fund further
development of the MySQL database.
MySQL partnership logos may be used only by companies and persons
having a written partnership agreement with MySQL AB. Partnerships
include certification as a MySQL trainer or consultant.
For more information, please see section 1.3.1.5 Partnering.
MySQL AB welcomes references to the MySQL database, but
it should be noted that the word MySQL is a trademark of MySQL AB.
Because of this, you must append the trademark symbol (TM) to
the first or most prominent use of the word MySQL in a text and,
where appropriate, state that MySQL is a trademark of
MySQL AB. For more information, please refer to our trademark policy at
http://www.mysql.com/company/trademark.html.
Use of the word MySQL in product or company names or in Internet
domain names is not allowed without written permission from MySQL AB.
This section provides a snapshot of the MySQL development roadmap, including
major features implemented or planned for MySQL 4.0, 4.1, and 5.0.
The following sections provide information for each release.
Plans for some of the most requested features are summarized in the following
table.
| Feature | MySQL version
|
| Unions | 4.0
|
| Subqueries | 4.1
|
| R-trees | 4.1 (for MyISAM tables)
|
| Stored procedures | 5.0
|
| Cursors | 5.0
|
| Foreign keys | 5.1 (3.23 with InnoDB)
|
| Views | 5.1
|
| Triggers | 5.1
|
| Full outer join | 5.1
|
| Constraints | 5.1
|
Long promised by MySQL AB and long awaited by our users,
MySQL Server 4.0 is now available in production version.
MySQL 4.0 is available for download from http://www.mysql.com/
and from our mirrors. MySQL 4.0 has been tested by a large number of users
and is in production use at many large sites.
The major new features of MySQL Server 4.0 are geared toward our existing
business and community users, enhancing the MySQL database software
as the solution for mission-critical, heavy-load database systems.
Other new features target the users of embedded databases.
MySQL Version 4.0.12 was declared stable for production use in
March 2003. This means that, in future, only bug fixes will be done for
the 4.0 release series and only critical bug fixes will be done for the
older 3.23 series.
See section 2.5.2 Upgrading From Version 3.23 to 4.0.
New features to the MySQL software are being added to MySQL 4.1
which is now also available (alpha version).
See section 1.5.2 MySQL 4.1 in a Nutshell.
- Speed enhancements
-
-
MySQL 4.0 has a query cache that can give a huge speed boost to
applications with repetitive queries. See section 6.9 MySQL Query Cache.
-
Version 4.0 further increases the speed of MySQL Server
in a number of areas, such as bulk
INSERTs, searching on
packed indexes, creation of FULLTEXT indexes, and COUNT(DISTINCT).
- Embedded MySQL Server introduced
-
-
The new Embedded Server library (instead of client/server) can easily
be used in standalone and embedded applications.
See section 1.5.1.2 Embedded MySQL Server.
- InnoDB storage engine as standard
-
-
The
InnoDB storage engine is now offered as a standard feature of the
MySQL server. This means full support for ACID transactions,
foreign keys with cascading UPDATE/DELETE, and row-level locking
are now standard features.
See section 7.5 InnoDB Tables.
- New functionality
-
-
The enhanced
FULLTEXT search properties of MySQL Server 4.0 enables
FULLTEXT indexing of large text masses with both binary
and natural-language searching logic. You can customise minimal word
length and define your own stop word lists in any human language,
enabling a new set of applications to be built on MySQL Server.
See section 6.8 MySQL Full-text Search.
- Standards compliance, portability, and migration
-
-
Features to simplify migration from other database systems to MySQL
Server include
TRUNCATE TABLE (as in Oracle).
-
Many users will also be happy to learn that MySQL Server now supports the
UNION statement, a long-awaited standard SQL feature.
-
MySQL can now run natively on the Novell NetWare 6.0 platform.
See section 2.6.8 Novell NetWare Notes.
- Internationalisation
-
-
Our German, Austrian, and Swiss users will note that
MySQL now
supports a new character set, latin1_de, which ensures that the
German sorting order sorts words with umlauts in the same order
as do German telephone books.
- Usability enhancements
-
In the process of building features for new users, we have not forgotten
requests from our community of loyal users.
-
Most
mysqld parameters (startup options) can now be set without taking
down the servers. This is a convenient feature for Database Administrators (DBAs).
See section 5.5.6 SET Syntax.
-
Multi-table
DELETE and UPDATE statements have been added..
-
Support has been added for
symbolic linking to MyISAM at the table
level (and not just the database level as before) and for enabling
symlink handling by default on Windows.
-
SQL_CALC_FOUND_ROWS and FOUND_ROWS() are new functions that make it
possible to find out the number of rows a SELECT query that includes a
LIMIT clause would have returned without that clause.
The news section of this manual includes a more in-depth list of features.
See section D.3 Changes in release 4.0.x (Production).
libmysqld makes MySQL Server suitable for a vastly expanded realm of
applications. Using the embedded MySQL server library, one can
embed MySQL Server into various applications and electronics devices, where
the end user has no knowledge of there actually being an underlying
database. Embedded MySQL Server is ideal for use behind
the scenes in Internet appliances, public kiosks, turnkey
hardware/software combination units, high performance Internet
servers, self-contained databases distributed on CD-ROM, and so on.
Many users of libmysqld will benefit from the MySQL
Dual Licensing. For those not wishing to be bound by the GPL,
the software is also made available under a commercial license.
The embedded MySQL library uses the same interface as the normal
client library, so it is convenient and easy to use. See section 9.1.15 libmysqld, the Embedded MySQL Server Library.
MySQL Server 4.0 laid the foundation for new features such as
nested subqueries and Unicode (implemented in version 4.1)
and for the work on SQL-99 stored procedures being done for
version 5.0. These features come at the top of the wish list of many
of our customers.
With these additions, critics of the MySQL Database Server have to be
more imaginative than ever in pointing out deficiencies in the MySQL
Database Management System. Already well-known for its stability,
speed, and ease of use, MySQL Server will be able to fulfill the requirement
checklists of very demanding buyers.
The features listed in this section are implemented in MySQL 4.1. A few other
features are still planned for MySQL 4.1. See section 1.8.1 New Features Planned For 4.1.
Most new features being coded, such as stored procedures,
will be available in MySQL 5.0. See section 1.8.2 New Features Planned For 5.0.
- Support for subqueries and derived tables
-
-
Subqueries are now supported. Here is an example:
SELECT * FROM t1 WHERE t1.a=(SELECT t2.b FROM t2);
SELECT * FROM t1 WHERE (1,2,3) IN (SELECT a,b,c FROM t2);
-
Derived tables (unnamed views) are now supported. Basically, a derived table
is a subquery in the
FROM clause of a SELECT statement. Here is
an example:
SELECT t1.a FROM t1, (SELECT * FROM t2) t3 WHERE t1.a=t3.a;
- Speed enhancements
-
-
Faster binary protocol with prepared statements and parameter binding.
See section 9.1.4 C API Prepared Statements.
-
BTREE indexing is now supported for HEAP tables,
significantly improving response time for non-exact searches.
- New functionality
-
-
CREATE TABLE table LIKE table allows you to create a new table
with the exact structure of an existing table, using a single command.
-
Support for OpenGIS spatial types (geographical data).
See section 11 Spatial Extensions in MySQL.
- Standards compliance, portability, and migration
-
-
The new client/server protocol adds the ability to pass multiple
warnings to the client, rather than only a single result. This
makes jobs such as bulk loading of data much easier to track.
SHOW WARNINGS shows warnings for the last command.
See section 4.5.7.9 SHOW WARNINGS | ERRORS.
- Internationalisation
-
-
To support our ever expanding user base using local languages
in applications, the MySQL software now offers extensive
Unicode (UTF8) support.
-
Character sets can now be defined per column, table, and database.
This allows for a high degree of flexibility in application design,
particularly for multi-language web sites.
-
For documentation for this improved character set support,
see section 8 National Character Sets and Unicode in MySQL 4.1.
- Usability enhancements
-
-
In response to popular demand, we have added a server-based
HELP command that can be used in the mysql command line
client (and other clients) to get help for SQL commands.
The advantage of having this information on the server side is that the
information is always applicable for that particular server version.
-
In the new client/server protocol, multi-line queries can now be enabled.
This allows you to issue several queries in a single call and then read
all the results in one go.
See section 9.1.8 C API Handling of Multiple Query Execution.
-
A new
INSERT ... ON DUPLICATE KEY UPDATE ... syntax has been
implemented. This allows you to UPDATE an existing row if the
INSERT would have caused a duplicate in a PRIMARY or
UNIQUE key (index).
See section 6.4.3 INSERT Syntax.
-
We have designed a new aggregate function
GROUP_CONCAT(),
adding the extremely useful capability of concatenating columns from
grouped rows into a single result string.
See section 6.3.7 Functions and Modifiers for Use with GROUP BY Clauses.
-
The new client/server protocol supports multiple result sets.
The news section in this manual includes a more in-depth list of features.
See section D.2 Changes in release 4.1.x (Alpha).
New features are being added to MySQL 4.1, which is already available
for download (alpha version). See section 1.5.2.3 Ready for Immediate Development Use.
The set of features that are being added to version 4.1 is mostly
fixed. Additional development is already ongoing for version 5.0.
MySQL 4.1 will go through the steps of
Alpha (during which time new features might still be added/changed),
Beta (when we have feature freeze and only bug corrections will be done),
and Gamma (indicating that a production release is just weeks ahead).
At the end of this process, MySQL 4.1 will become the new production release.
MySQL 4.1 is currently in the alpha stage, and binaries are available
for download at http://www.mysql.com/downloads/mysql-4.1.html.
All binary releases pass our extensive test suite without any errors on
the platforms on which we test.
See section D.2 Changes in release 4.1.x (Alpha).
For those wishing to use the most recent development source for MySQL 4.1,
we have made our 4.1 BitKeeper repository publicly available.
See section 2.3.4 Installing from the Development Source Tree.
New development for MySQL is focused on the 5.0 release, featuring
Stored Procedures and other new features.
See section 1.8.2 New Features Planned For 5.0.
For those wishing to take a look at the bleeding edge of MySQL
development, we have made our BitKeeper repository for
MySQL version 5.0 publicly available.
See section 2.3.4 Installing from the Development Source Tree.
This section introduces you to the MySQL mailing lists and gives
some guidelines as to how the lists should be used. When you subscribe to a mailing
list, you will receive, as e-mail messages, all postings to the list. You will
also be able to send your own questions and answers to the list.
To subscribe to or unsubscribe from any of the mailing lists described in this
section, visit http://lists.mysql.com/.
Please do not send messages about
subscribing or unsubscribing to any of the mailing lists, because such
messages are distributed automatically to thousands of other users.
Your local site may have many subscribers to a MySQL mailing list.
If so, the site 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.
If you wish to have traffic for a mailing list go to a separate mailbox in
your mail program, set up a filter based on the message headers. You can
use either the List-ID: or Delivered-To: headers to identify
list messages.
The MySQL mailing lists are as follows:
announce-
This list is for announcements of new versions of MySQL and related
programs. This is a low-volume list to which all MySQL users should
subscribe.
mysql-
This is the main list for general MySQL discussion. Please note that some
topics are better discussed on the more-specialised lists. If you post to the
wrong list, you may not get an answer.
mysql-digest-
This is the
mysql list in digest form. Subscribing to this list means
you will get all list messages, sent as one large mail message once a day.
bugs-
This list will be of interest to you if you want to stay informed about
issues reported since the last release of
MySQL or if you want to be
actively involved in the process of bug hunting and fixing.
See section 1.6.1.3 How to Report Bugs or Problems.
bugs-digest-
This is the
bugs list in digest form.
internals-
This list is for people who work on the MySQL code. This is also the
forum for discussions on MySQL development and post patches.
internals-digest-
This is the
internals list in digest form.
mysqldoc-
This list is for people who work on the MySQL documentation:
people from MySQL AB, translators, and other community members.
mysqldoc-digest-
This is the
mysqldoc list in digest form.
benchmarks-
This list is for anyone interested in performance issues. Discussions
concentrate on database performance (not limited to MySQL) but also
include broader categories such as performance of the kernel,
file system, disk system, and so on.
benchmarks-digest-
This is the
benchmarks list in digest form.
packagers-
This list is for discussions on packaging and distributing MySQL. This is the
forum used by distribution maintainers to exchange ideas on packaging MySQL
and on ensuring that MySQL looks and feels as similar as possible on all
supported platforms and operating systems.
packagers-digest-
This is the
packagers list in digest form.
java-
This list is for discussions about the MySQL server and Java.It is mostly
used to discuss JDBC drivers, including MySQL Connector/J.
java-digest-
This is the
java list in digest form.
win32-
This list is for all things concerning the MySQL software on Microsoft
operating systems, such as Windows 9x/Me/NT/2000/XP.
win32-digest-
This is the
win32 list in digest form.
myodbc-
This list is for all things concerning connecting to the MySQL server with ODBC.
myodbc-digest-
This is the
myodbc list in digest form.
mysqlcc-
This list is for all things concerning the
MySQL Control Center graphical client.
mysqlcc-digest-
This is the
mysqlcc list in digest form.
plusplus-
This list is for all things concerning programming with the C++ API to MySQL.
plusplus-digest-
This is the
plusplus list in digest form.
msql-mysql-modules-
This list is for all things concerning the Perl support for MySQL with
msql-mysql-modules,
which is now named DBD-mysql.
msql-mysql-modules-digest-
This is the
msql-mysql-modules list in digest form.
If you're unable to get an answer to your question(s) from a MySQL mailing list, one
option is to pay for support from MySQL AB. This will put you
in direct contact with MySQL developers. See section 1.4.1 Support Offered by MySQL AB.
The following table shows some MySQL mailing lists in languages other than
English. These lists are not operated by MySQL AB, so we can't
guarantee their quality.
mysql-france-subscribe@yahoogroups.com A French mailing list
-
list@tinc.net A Korean mailing list
-
E-mail
subscribe mysql your@e-mail.address to this list.
mysql-de-request@lists.4t2.com A German mailing list
-
E-mail
subscribe mysql-de your@e-mail.address to this list.
You can find information about this mailing list at
http://www.4t2.com/mysql/.
mysql-br-request@listas.linkway.com.br A Portuguese mailing list
-
E-mail
subscribe mysql-br your@e-mail.address to this list.
mysql-alta@elistas.net A Spanish mailing list
-
E-mail
subscribe mysql your@e-mail.address to this list.
Before posting a bug report or question, please do the following:
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, please follow the guidelines on sending mail to a MySQL mailing list,
outlined in the next section, before contacting us.
Our bugs database is public, and can be browsed and searched by anyone
at http://bugs.mysql.com/.
If you log into the system, you will also be able to enter new reports.
Writing a good bug report takes patience, but doing it right the first
time saves time both for us and for yourself. A good bug report, containing
a full test case for the bug, makes it very likely that we will fix the bug 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). mysqlbug can be
found in the `scripts' directory (source distribution) and in the
`bin' directory under your MySQL installation directory (binary distribution).
If you are unable to use mysqlbug (for instance, if you are running
on Windows), it is still vital that you include all the necessary information
noted in this section (most importantly a description of the operating system
and the MySQL version).
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.
Preferably, you should test the problem using the latest production or
development version of MySQL Server 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 in the bugs database at http://bugs.mysql.com/
will be corrected or documented in the
next MySQL release. If only minor code changes are needed to correct a
problem, we will also post a patch that fixes the problem.
The normal place to report bugs is http://bugs.mysql.com/.
If you have found a sensitive security bug in MySQL, please send an
e-mail to security@mysql.com.
If you have a repeatable bug report, please report this into the bugs
database at http://bugs.mysql.com/. Note that even in this case
it's good to run the mysqlbug script first to find information
about your system. Any bug that we are able to repeat has a high chance
of being fixed in the next MySQL release.
To report other problems, you can use one of the MySQL mailing lists.
Remember that it is possible for us to respond to a message containing too much
information, but not to one containing too little. People often 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 made in bug reports are (a) not including the version number of
the MySQL distribution used and (b) not fully describing the platform on which the MySQL server
is installed (including the platform type and 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 already been fixed in newer MySQL
versions. Sometimes the error is platform-dependent; in such cases, it is
next to impossible for us 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 your
problem depends on your compiler, we need to know what compiler you use.
Note that every compiling problem should be regarded as a bug and
reported accordingly.
It is most helpful when a good description of the problem is included in the
bug report. That is, give a good example of all the things you did that led to
the problem and describe, in exact detail, the problem itself. The best reports are
those that include a full example showing how to reproduce the bug or
problem. See section E.1.6 Making a Test Case If 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, please try to generate a MyODBC
trace file and send it with your report. See section 9.2.7 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 later in this section).
Please include the following information in your report:
-
The version number of the MySQL distribution you are using (for
example, MySQL Version 4.0.12). 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 on which you experience the
problem.
-
The operating system name and version. For most operating systems, you can
get this information by executing the Unix command
uname -a. If
you work with Windows, you can usually get the name and version number
by double-clicking your ''My Computer'' icon and pulling down the ''Help/About Windows''
menu.
-
Sometimes the amount of memory (real and virtual) is relevant. If in doubt,
include these values.
-
If you are using a source distribution of the MySQL software, 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 occurrs.
-
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 E.1.5 Using Log Files to Find Cause of Errors in mysqld.
-
If a 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.
The information 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. You
should also include the output from SHOW CREATE TABLE tbl_name
for each involved table. The more information you give about your
situation, the more likely it is that someone can help you. 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 reproducible test case, you should
post it on http://bugs.mysql.com/ for 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 on how your system is performing.
-
If you can't produce a test case with only 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 enter
the problem into our bugs database at http://bugs.mysql.com/.
-
If you think that the MySQL server 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 is really top
secret and you don't want to show it 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 as well as the options 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. 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, do include it. 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 bug report that you have checked the reference manual
and mail archive so that others know 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 Server doesn't support the syntax you are
using. If you are using the current version and the manual at
http://www.mysql.com/doc/ doesn't cover the
syntax you are using, MySQL Server doesn't support your query. In this
case, your only options are to implement the syntax yourself or e-mail
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 Server, 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 Server. See section D MySQL Change History.
-
If your problem is that your data appears corrupt or you get
errors when you access a particular table, you should first check and then
try repairing your tables with
myisamchk or CHECK TABLE and
REPAIR TABLE. See section 4 Database Administration.
-
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 4.9.1 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 A.1 How to Determine What Is Causing Problems.
-
If possible, download and install the most recent version of MySQL Server
and check whether it solves your problem. All versions of
the MySQL software 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 without difficulty.
See section 2.2.6 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 9.2.4 How to Report Problems with MyODBC.
For solutions to some common problems, see section A Problems and Common Errors.
When answers are sent to you individually and not to the mailing list,
it is considered good etiquette to summarise 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.
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 summarise 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.
In addition to the various MySQL mailing lists, you can find experienced
community people on IRC (Internet Relay Chat).
These are the best networks/channels currently known to us:
- freenode (see http://www.freenode.net/ for servers)
#mysql
Primarily MySQL questions but other database and SQL questions welcome.
#mysqlphp
Questions about MySQL+PHP, a popular combination.
#mysqlperl
Questions about MySQL+Perl, another popular combination.
- EFnet (see http://www.efnet.org/ for servers)
If you are looking for IRC client software to connect to an IRC network,
take a look at X-Chat (http://www.xchat.org/).
X-Chat (GPL licensed) is available for Unix as well as for Windows platforms.
This section describes how MySQL relates to the ANSI/ISO SQL standards.
MySQL Server has many extensions to the SQL standard, and here you
will find out what they are and how to use them. You will also find
information about functionality missing from MySQL Server, and how to work
around some differences.
Our goal is to not, without a very good reason, restrict MySQL Server usability
for any usage. Even if we don't have the resources to do development
for every possible use, we are always willing to help and offer
suggestions to people who are trying to use MySQL Server in new territories.
One of our main goals with the product is to continue to work toward
compliance with the SQL-99 standard, but without sacrificing speed or reliability.
We are not afraid to add extensions to SQL or support for non-SQL
features if this greatly increases the usability of MySQL Server for a big
part of our users. (The new HANDLER interface in MySQL Server 4.0
is an example of this strategy. See section 6.4.2 HANDLER Syntax.)
We will continue to support transactional and non-transactional
databases to satisfy both heavy web/logging usage and mission-critical
24/7 usage.
MySQL Server was designed from the start to work with medium size databases
(10-100 million rows, or about 100 MB per table) on small computer
systems. We will continue to extend MySQL Server to work even better
with terabyte-size databases, as well as to make it possible
to compile a reduced MySQL version that is more suitable for hand-held
devices and embedded usage. The compact design of the MySQL server makes both
of these directions possible without any conflicts in the source tree.
We are currently not targeting realtime support or clustered databases
(even if you can already do a lot of things with our replication
services).
We are looking at providing XML support in the database server.
Entry-level SQL-92. ODBC levels 0-3.51.
We are aiming toward supporting the full SQL-99 standard,
but without concessions to speed and quality of the code.
|
