MySQL Reference Manual for version 4.0.18.
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.fsf.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 Overview of 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 D Porting to Other Systems.
-
For information about upgrading from a Version 4.0 release, see
section 2.5.2 Upgrading from Version 4.0 to 4.1.
-
For information about upgrading from a Version 3.23 release, see
section 2.5.3 Upgrading from Version 3.23 to 4.0.
-
For information about upgrading from a Version 3.22 release, see
section 2.5.4 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 C MySQL Change History.
-
For a list of currently known bugs and misfeatures, see section 1.8.7 Known Errors and Design Deficiencies in MySQL.
-
For future plans, see section 1.6 MySQL and the Future (The TODO).
-
For a list of all the contributors to this project, see section B 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 1.7.1.1 The MySQL Mailing Lists.
See section 1.7.1.3 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, please let
us know immediately by sending an email message to security@mysql.com.
This is the MySQL reference manual; it documents MySQL
up to Version 4.0.18. 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. It also will not teach you how to
use your operating system or command line interpreter.
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.
The index can assist you in finding information in the manual. For online use,
you can try the searchable version of the manual available 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 B Credits.
The copyright (2004) 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 statement that you execute from the
mysql client program:
shell> type a shell command here
mysql> type a mysql statement here
The ``shell'' is your command interpreter. On Unix, this is typically a
program such as sh or csh. On Windows, the equivalent is
command.com or cmd.exe, typically run in a Windows console.
Note that to enter a command or statement from an example, you do not type
the prompt shown in the example.
Commands to set shell variables are shown using Bourne shell syntax. If you
are using csh or tcsh, you will need to issue commands somewhat
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 or tcsh, 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}
An ellipsis (...) indicates the omission of a section of a statement,
typically to provide a shorter version of more complex syntax. For example,
INSERT ... SELECT is shorthand for the form of INSERT statement
that is followed by a SELECT statement.
An ellipsis can also indicate that the preceding syntax element of a statement
may be repeated. In the following example, multiple reset_option values
may be given, with each of those after the first preceded by commas:
RESET reset_option [,reset_option] ...
MySQL, the most popular Open Source SQL database management
system, is
developed, distributed, and supported by MySQL AB. MySQL AB is a
commercial company, founded by the MySQL developers, that builds its business
by providing services around the MySQL database management system.
See section 1.3 Overview of 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 standardized 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 next version of the standard.
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.fsf.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 7.1.4 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
-
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 application 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 localized 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 or
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
designed to allow third-party code that was written for use with mSQL to
be ported easily for use with MySQL.
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
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 2.1.1 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 are available.
See section 19 MySQL APIs.
-
Fully multi-threaded using kernel threads. This means it can easily
use multiple CPUs if they are available.
-
Provides transactional and non-transactional storage engines.
-
Uses 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 optimized one-sweep multi-join.
-
In-memory hash tables which are used as temporary tables.
-
SQL functions are implemented using a highly optimized class library and
should be as fast as possible. Usually there is no memory allocation
at all after query initialization.
-
The
MySQL code is tested with Purify
(a commercial memory leakage detector) as well as with Valgrind,
a GPL tool (http://developer.kde.org/~sewardj/).
-
The server is available as a separate program for use in a client/server
networked environment. It is also available as a library that can be
embedded (linked) into standalone applications. Such applications can be
used in isolation or in environments where no network is available.
- 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, ENUM, and OpenGIS geometry
types.
See section 11 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 column.
- Connectivity
-
-
Clients may connect to the
MySQL server using TCP/IP sockets
on any platform. On Windows systems in the NT family (NT, 2000,
or XP), clients may connect using named pipes. On Unix systems,
clients may connect using Unix domain socket files.
-
The Connector/ODBC interface provides
MySQL support for client programs
that use ODBC (Open-DataBase-Connectivity) connections. For example,
you can use MS Access to connect to your MySQL server. Clients may
be run on Windows or Unix. Connector/ODBC source is available. All ODBC
2.5 functions are supported, as are many others.
See section 19.2 MySQL ODBC Support.
-
The Connector/JDBC interface provides
MySQL support for Java client
programs that use JDBC connections. Clients may be run on Windows or Unix.
Connector/JDBC source is available.
See section 19.3 MySQL Java Connectivity (JDBC).
- Localization
-
-
The server can provide error messages to clients in many languages.
See section 5.7.2 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.
Unicode support is available as of
MySQL 4.1.
-
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
-
-
The MySQL server has built-in support for SQL statements to check,
optimize, and repair tables. These statements are available from the
command line through the
mysqlcheck client. MySQL also includes
myisamchk, a very fast command-line utility for performing these
operations on MyISAM tables.
See section 5 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.
The original code stems back to the early 1980s. It provides a stable code
base, and the ISAM table format used by the original storage engine
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 initially 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 design-related. See section 1.8.7 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 groups of servers using replication are in production use, with
good results. Work on enhanced replication features is continuing
in
MySQL 5.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.
- Full-text searches -- Beta
-
Full-text searching works but is not yet widely used.
Important enhancements have been implemented in
MySQL 4.0.
Connector/ODBC 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 operating system 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.
Paying customers receive high-quality support directly from MySQL AB.
MySQL AB also provides the MySQL mailing list as a community resource
where anyone may ask 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 storage engine in MySQL Version 3.23, the maximum table
size was increased to 8 million terabytes (2 ^ 63 bytes). With this larger
allowed table size, the maximum effective table size for MySQL
databases now normally is determined by operating system constraints
on file sizes, not by MySQL internal limits.
The InnoDB storage engine maintains InnoDB tables within a
tablespace that can be created from several files. This allows a
table to exceed the maximum individual file size. The tablespace can include
raw disk partitions, which allows extremely large tables. The maximum
tablespace size is 64 TB.
The following table lists some examples of operating system file-size
limits:
| 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 (4GB possible 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 MyISAM 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 Linux
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 creates MyISAM tables with an internal
structure that allows 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 13.5.3 SHOW Syntax.
If you need a MyISQM table that will be larger than 4 GB in size (and your
operating system supports large files), the CREATE TABLE statement
allows AVG_ROW_LENGTH and MAX_ROWS options.
See section 13.2.5 CREATE TABLE Syntax.
You can also change these options with ALTER TABLE after the table has
been created, to increase the table's maximum allowable size.
See section 13.2.2 ALTER TABLE Syntax.
Other ways to work around file-size limits for MyISAM tables are as
follows:
-
If your large table is read-only, you can use
myisampack to
compress it. myisampack usually compresses a table by at
least 50%, so you can have, in effect, much bigger tables.
myisampack also can merge multiple tables into a single table.
See section 8.11 myisampack, The MySQL Compressed Read-only Table Generator.
-
Another way to get around the operating system file limit for
MyISAM
datafiles is by using the RAID options.
See section 13.2.5 CREATE TABLE Syntax.
-
MySQL includes a MERGE library that allows
you to handle a collection of MyISAM tables that have identical
structure as a single MERGE table.
See section 14.2 MERGE Tables.
The MySQL Server itself has no problems with Year 2000 (Y2K)
compliance:
-
MySQL Server uses Unix time functions that handle dates into the year
2037 for TIMESTAMP values. For DATE and DATETIME
values, dates through the year 9999 are accepted.
-
All
MySQL date functions are implemented in one source 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.
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.
The following simple demonstration illustrates that MySQL Server
doesn't have any problems with dates until after 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)
The final TIMESTAMP column value is zero because the final
year (2050) exceeds the TIMESTAMP maximum. 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).
The example also shows that the DATE and DATETIME datatypes have
no problems with the dates used. They handle dates through the year
9999.
Although MySQL Server itself is Y2K-safe, you may run into
problems if you use it with applications that are 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.
Thus, even though MySQL Server has no Y2K problems, it is
the application's responsibility to provide unambiguous input.
See section 11.2.1 Y2K Issues and Date Types for MySQL Server's rules for dealing
with ambiguous date input data that contains 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 organization with people in a dozen countries around
the world. We communicate extensively over the Internet every day with one another
and with our users, supporters, and partners.
We are dedicated to developing the MySQL database software and
promoting it 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 Overview of the MySQL Database Management System.
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 email 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 providing support
to customers and other users in order to stay in touch with their needs
and problems. All our support is provided 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 Authorized 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 applications.
-
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 Authorized 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 14.4 InnoDB Tables.
MySQL AB has a worldwide partner program 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 email
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 December 2003, we served 16 million page views.
Our visitors represent a group that makes purchase decisions and
recommendations for both software and hardware. Twelve percent of our
visitors authorize 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 email 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 email message 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 email 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 email 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 email
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 email 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 email 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 email to jobs@mysql.com.
Please do not send your CV as an attachment, but rather as plain text
at the end of your email message.
For general discussion among our many users, please direct your
attention to the appropriate mailing list.
See section 1.7.1 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 1.7.1.1 The MySQL Mailing Lists.
If you have found a sensitive security bug in MySQL Server, please let
us know immediately by sending an email message to security@mysql.com.
See section 1.7.1.3 How to Report Bugs or Problems.
If you have benchmark results that we can publish, please
contact us via email at benchmarks@mysql.com.
If you have suggestions concerning additions or corrections to this
manual, please send them to the manual team via email at docs@mysql.com.
For questions or comments about the workings or content of the
MySQL web site (http://www.mysql.com/),
please send email 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 email to
privacy@mysql.com.
For all other inquires, please send an email to info@mysql.com.
This section describes MySQL support and licensing arrangements.
Technical support from MySQL AB means individualized 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 the impact of operating system or networking issues
on MySQL,
set up best practices for backup and recovery, utilize 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 email at sales@mysql.com.
Technical support is like life insurance. You can live happily
without it for years. However, when your hour arrives, it becomes
critically important, but 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 Overview of 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 G 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 http://www.fsf.org/licenses/.
-
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 email message 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.fsf.org/licenses/.
See also http://www.fsf.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 email 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.fsf.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 management system, which is like 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 colors 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 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 email 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, 5.0, and 5.1.
The following sections provide information for each release series.
The production release series is MySQL 4.0, which was declared stable
for production use as of Version 4.0.12, released in March 2003. This
means that future 4.0 development will be limited only to making bug
fixes. For the older MySQL 3.23 series, only critical bug fixes will
be made.
Active MySQL development currently is taking place in the MySQL 4.1 and
5.0 release series. This means that new features are being added to MySQL
4.1 and MySQL 5.0. Both 4.1 and 5.0 are available now in alpha status.
Before upgrading from one release series to the next, please see the notes
at section 2.5 Upgrading/Downgrading MySQL.
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
|
| Views | 5.0 or 5.1
|
| Cursors | 5.0
|
| Foreign keys | 5.1 (already implemented in 3.23 for InnoDB)
|
| Triggers | 5.1
|
| Full outer join | 5.1
|
| Constraints | 5.1
|
Long awaited by our users, MySQL Server 4.0 is now available in production
status.
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.
- Speed enhancements
-
-
MySQL 4.0 has a query cache that can give a huge speed boost to
applications with repetitive queries. See section 13.8 MySQL Query Cache.
-
Version 4.0 further increases the speed of MySQL Server
in a number of areas, such as bulk
INSERT statements, searching on
packed indexes, full-text searching (using FULLTEXT indexes), and
COUNT(DISTINCT).
- Embedded MySQL Server introduced
-
-
The new Embedded Server library can easily be used to create standalone and
embedded applications. The embedded server provides an alternative to using
MySQL in a client/server environment.
See section 1.5.1.2 The 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 and DELETE, and row-level locking
are now standard features.
See section 14.4 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 customize minimal word
length and define your own stop word lists in any human language,
enabling a new set of applications to be built with MySQL Server.
See section 13.7 MySQL Full-text Search.
- Standards compliance, portability, and migration
-
-
Many users will also be happy to learn that MySQL Server now supports the
UNION statement, a long-awaited standard SQL feature.
-
MySQL now runs natively on the Novell NetWare 6.0 platform.
See section 2.2.4 Installing MySQL on NetWare.
-
Features to simplify migration from other database systems to MySQL
Server include
TRUNCATE TABLE (as in Oracle).
- Internationalization
-
-
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 implementing features for new users, we have not forgotten
requests from our loyal community of existing users.
-
Most
mysqld parameters (startup options) can now be set without taking
down the server. This is a convenient feature for database administrators
(DBAs).
See section 7.5.6 SET Syntax.
-
Multiple-table
DELETE and UPDATE statements have been added..
-
On Windows, symbolic link handling at the database level is enabled by default.
On Unix, the
MyISAM storage engine now supports symbolic
linking at the table level (and not just the database level as before).
-
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 C.3 Changes in release 4.0.x (Production).
The libmysqld embedded server library makes MySQL Server suitable for
a vastly expanded realm of applications. By using this library, developers 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 19.1.15 libmysqld, the Embedded MySQL Server Library.
MySQL Server 4.0 laid the foundation for new features implemented in MySQL
4.1, such as subqueries and Unicode support,
and for the work on stored procedures being done in 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 1.6.1 New Features Planned for 4.1.
Most new features being coded are or will be available in MySQL 5.0.
See section 1.6.2 New Features Planned for 5.0.
- Support for subqueries and derived tables
-
-
A subquery is a
SELECT statement nested within another statement.
A derived table (an unnamed view) is a subquery in the FROM clause
of another statement.
See section 13.1.8 Subquery Syntax.
- Speed enhancements
-
-
Faster binary client/server protocol with support for prepared statements
and parameter binding.
See section 19.1.4 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_name2 LIKE table_name1 allows you to create, with
a single statement, a new table with a structure exactly like that of an
existing table.
-
The MyISAM storage engine now supports
OpenGIS spatial types for storing geographical data.
See section 17 Spatial Extensions in MySQL.
-
Replication can be done over SSL connections.
- 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 operations such as bulk data loading much easier to track.
-
SHOW WARNINGS shows warnings for the last command.
See section 13.5.3.9 SHOW WARNINGS | ERRORS.
- Internationalization
-
-
To support applications that require the use of local languages,
the MySQL software now offers extensive
Unicode support through the
utf8 and ucs2 character sets.
-
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 16 National Character Sets and Unicode.
- Usability enhancements
-
-
In response to popular demand, we have added a server-based
HELP command that can be used
to get help information for SQL statements.
The advantage of having this information on the server side is that the
information is always applicable to the particular server version that you
actually are using.
Because this information is available by issuing a SQL statement, any client
can be written to access it.
For example, the help command of the mysql command-line client
has been modified to have this capability.
-
In the new client/server protocol, multiple statements can be issued with
a single call.
See section 19.1.8 C API Handling of Multiple Query Execution.
-
The new client/server protocol also supports returning multiple result sets.
This might occur as a result of sending multiple statements, for example.
-
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 13.1.4 INSERT Syntax.
-
A new aggregate function,
GROUP_CONCAT()
adds the extremely useful capability of concatenating column values from
grouped rows into a single result string.
See section 12.7 Functions and Modifiers for Use with GROUP BY Clauses.
The news section of this manual includes a more in-depth list of features.
See section C.2 Changes in release 4.1.x (Alpha).
New features are being added to MySQL 4.1. The alpha version is already
available for download. 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 C.2 Changes in release 4.1.x (Alpha).
For those wishing to use the most recent development source for MySQL 4.1,
we make our 4.1 BitKeeper repository publicly available.
See section 2.3.3 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 1.6.2 New Features Planned for 5.0.
For those wishing to take a look at the bleeding edge of MySQL
development, we make our BitKeeper repository for
MySQL version 5.0 publicly available.
See section 2.3.3 Installing from the Development Source Tree.
As of December 2003, binary builds of version 5.0 are also available.
This section summarizes the features that we plan to implement in
MySQL Server. The items are ordered by release series. Within a list,
items are shown in approximately the order they will be done.
Note: If you are an enterprise level user with an urgent need
for a particular feature, please contact sales@mysql.com to
discuss sponsoring options. Targeted financing by sponsor companies
allows us to allocate additional resources for specific purposes.
One example of a feature sponsored in the past is replication.
The features below are not yet implemented in MySQL 4.1, but are planned
for implementation before MySQL 4.1 moves into its beta phase.
For a list what is already done in MySQL 4.1, see section 1.5.2.1 Features Available in MySQL 4.1.
-
Stable OpenSSL support (MySQL 4.0 supports rudimentary, not 100% tested,
support for OpenSSL).
-
More testing of prepared statements.
-
More testing of multiple character sets for one table.
The following features are planned for inclusion into MySQL 5.0.
Some of the features such as stored procedures are complete and are
included in MySQL 5.0 alpha, which is available now. Others such
as cursors are only partially available. Expect these and other
features to mature and be fully supported in upcoming releases.
Note that because we have many developers that are working on different
projects, there will also be many additional features. There is also a
small chance that some of these features will be added to MySQL 4.1.
For a list what is already done in MySQL 4.1, see section 1.5.2.1 Features Available in MySQL 4.1.
For those wishing to take a look at the bleeding edge of MySQL
development, we make our BitKeeper repository for
MySQL version 5.0 publicly available.
See section 2.3.3 Installing from the Development Source Tree.
As of December 2003, binary builds of version 5.0 are also available.
- Stored Procedures
-
-
Stored procedures are currently implemented, based on the SQL:2003
standard.
See section 18 Stored Procedures and Functions.
We will also implement a framework to hook in external languages,
and (where possible) compatibility with, for example, PL/SQL and T-SQL.
- New functionality
-
-
Elementary cursor support.
See section 18.1.8 Cursors.
-
The ability to specify explicitly for
MyISAM tables that an index
should be created as an RTREE index. (In MySQL 4.1, RTREE indexes
are used internally for geometrical data that use GIS datatypes, but cannot be
created on request.)
-
Dynamic length rows for
HEAP tables.
- Standards compliance, portability and migration
-
-
Add true
VARCHAR support (column lengths longer than 255, and
no stripping of trailing whitespace).
(There is already support for this in the MyISAM storage engine,
but it is not yet available at the user level.)
- Speed enhancements
-
-
SHOW COLUMNS FROM table_name (used by mysql client to allow
expansions of column names) should not open the table, only the
definition file. This will require less memory and be much faster.
-
Allow
DELETE on MyISAM tables to use the record cache.
To do this, we need to update the threads record cache when we update
the `.MYD' file.
-
Better support for
MEMORY (HEAP) tables:
-
Dynamic length rows.
-
Faster row handling (less copying).
- Usability enhancements
-
-
Resolving the issue of
RENAME TABLE on a table used in an active
MERGE table possibly corrupting the table.
The news section of this manual includes a more in-depth list of features.
See section C.1 Changes in release 5.0.x (Development).
- New functionality
-
-
FOREIGN KEY support for all table types, not just InnoDB.
-
Column-level constraints.
-
Fail-safe replication.
-
Online backup with very low performance penalty. The online backup will
make it easy to add a new replication slave without taking down the
master.
- Speed enhancements
-
-
New text based table definition file format (`.frm' files) and a
table cache for table definitions. This will enable us to do faster
queries of table structures and do more efficient foreign key support.
-
Optimize the
BIT type to take 1 bit. (BIT now takes 1 byte;
it is treated as a synonym for TINYINT.)
- Usability enhancements
-
-
Add options to the client/server protocol to get progress notes
for long running commands.
-
Implement
RENAME DATABASE. To make this safe for all storage engines,
it should work as follows:
-
Create the new database.
-
For every table do a rename of the table to another database, as
we do with the
RENAME command.
-
Drop the old database.
-
New internal file interface change. This will make all file handling much
more general and make it easier to add extensions like RAID.
- New functionality
-
-
Oracle-like
CONNECT BY PRIOR ... to search tree-like (hierarchical)
structures.
-
Add all missing SQL-92 and ODBC 3.0 types.
-
Add
SUM(DISTINCT).
-
INSERT SQL_CONCURRENT and mysqld --concurrent-insert to do
a concurrent insert at the end of a table if the table is read-locked.
-
Allow variables to be updated in
UPDATE statements. For example:
UPDATE TABLE foo SET @a=a+b,a=@a, b=@a+c.
-
Change when user variables are updated so that one can use them with
GROUP BY, as in the following example:
SELECT id, @a:=COUNT(*), SUM(sum_col)/@a FROM table_name GROUP BY id.
-
Add an
IMAGE option to LOAD DATA INFILE to not update
TIMESTAMP and AUTO_INCREMENT fields.
-
Add
LOAD DATA INFILE ... UPDATE syntax that works like this:
-
For tables with primary keys, if an input record contains a primary key
value, existing rows matching that primary key value are updated from the
remainder of the input columns. However, columns corresponding to columns
that are missing from the input record are not touched.
-
For tables with primary keys, if an input record does not contain the primary
key value or is missing some part of the key, the record is treated as
LOAD DATA INFILE ... REPLACE INTO.
-
Make
LOAD DATA INFILE understand syntax like:
LOAD DATA INFILE 'file_name.txt' INTO TABLE tbl_name
TEXT_FIELDS (text_field1, text_field2, text_field3)
SET table_field1=CONCAT(text_field1, text_field2),
table_field3=23
IGNORE text_field3
This can be used to skip over extra columns in the text file,
or update columns based on expressions of the read data.
-
New functions for working with
SET type columns:
ADD_TO_SET(value,set)
REMOVE_FROM_SET(value,set)
-
If you abort
mysql in the middle of a query, you should open
another connection and kill the old running query.
Alternatively, an attempt should be made to detect this in the server.
-
Add a storage engine interface for table information so that you can use it as a system
table. This would be a bit slow if you requested information about all tables,
but very flexible.
SHOW INFO FROM tbl_name for basic table information
should be implemented.
-
Allow
SELECT a FROM table_name1 LEFT JOIN table_name2 USING (a); in this
case a is assumed to come from the table_name1 table.
-
DELETE and REPLACE options to the UPDATE statement
(this will delete rows when one gets a duplicate key error while updating).
-
Change the format of
DATETIME to store fractions of seconds.
-
Make it possible to use the new GNU
regexp library instead of the current
one (the new library should be much faster than the current one).
- Standards compliance, portability and migration
-
- Speed enhancements
-
-
Don't allow more than a defined number of threads to run
MyISAM
recovery at the same time.
-
Change
INSERT ... SELECT to optionally use concurrent inserts.
-
Add an option to periodically flush key pages for tables with delayed
keys if they haven't been used in a while.
-
Allow join on key parts (optimization issue).
-
Add a log file analyzer that can parse out information about which tables
are hit most often, how often multiple-table joins are executed, etc. This
should help users identify areas of table design that could be optimized
to execute much more efficient queries.
- Internationalization
-
- Usability enhancements
-
-
Return the original column types when doing
SELECT MIN(column) ... GROUP BY.
-
Make it possible to specify
long_query_time with a granularity
in microseconds.
-
Link the
myisampack code into the server so that it can perform
PACK or COMPRESS operations.
-
Add a temporary key buffer cache during
INSERT/DELETE/UPDATE so that we
can gracefully recover if the index file gets full.
-
If you perform an
ALTER TABLE on a table that is symlinked to another
disk, create temporary tables on that disk.
-
Implement a
DATE/DATETIME type that handles time zone information
properly, to make dealing with dates in different time zones easier.
-
Fix
configure so that one can compile all libraries (like MyISAM)
without threads.
-
Allow SQL variables as
LIMIT arguments, for example,
LIMIT @a,@b.
-
Automatic output from
mysql to a web browser.
-
LOCK DATABASES (with various options).
-
Many more variables for
SHOW STATUS. Records reads and
updates. Selects on a single table and selects with joins. Mean number of
tables in select. Number of ORDER BY and GROUP BY queries.
-
mysqladmin copy database new-database; this requires a COPY
operation to be added to mysqld.
-
Processlist output should indicate the number of queries/threads.
-
SHOW HOSTS for printing information about the hostname cache.
-
Change table names from empty strings to
NULL for calculated columns.
-
Don't use
Item_copy_string on numerical values to avoid
number->string->number conversion in case of:
SELECT COUNT(*)*(id+0) FROM table_name GROUP BY id
-
Change so that
ALTER TABLE doesn't abort clients
that execute INSERT DELAYED.
-
Fix so that when columns are referenced in an
UPDATE clause,
they contain the old values from before the update started.
- New operating systems
-
-
Port the MySQL clients to LynxOS.
-
Implement function:
get_changed_tables(timeout,table1,table2,...).
-
Change reading through tables to use memmap when possible. Now only
compressed tables use memmap.
-
Make the automatic timestamp code nicer. Add timestamps to the update
log with
SET TIMESTAMP=#;.
-
Use read/write mutex in some places to get more speed.
-
Simple views (implemented in stepwise fashion up to full functionality).
See section 1.8.5.6 Views.
-
Automatically close some tables if a table, temporary table, or temporary file
gets error 23 (too many open files).
-
Better constant propagation. When an occurrence of
col_name=n
is found in an expression, for some constant n, replace other
occurrences of col_name within the expression with n.
Currently, this is done only for some simple cases.
-
Change all const expressions with calculated expressions if possible.
-
Optimize key = expression comparisons. At the moment only key = field or
key = constant comparisons are optimized.
-
Join some of the copy functions for nicer code.
-
Change `sql_yacc.yy' to an inline parser to reduce its size and get
better error messages.
-
Change the parser to use only one rule per different number of arguments
in function.
-
Use of full calculation names in the order part (for ACCESS97).
-
MINUS, INTERSECT, and FULL OUTER JOIN.
(Currently UNION [in 4.0] and LEFT|RIGHT OUTER JOIN are supported.)
-
Allow
SQL_OPTION MAX_SELECT_TIME=#, for placing a time limit on a query.
-
Allow updates to be logged to a database.
-
Enhance
LIMIT to allow retrieval of data from the end of a result set.
-
Alarm around client connect/read/write functions.
-
Please note the changes to
mysqld_safe: according to FSSTND (which
Debian tries to follow) PID files should go into `/var/run/<progname>.pid'
and log files into `/var/log'. It would be nice if you could put the
"DATADIR" in the first declaration of "pidfile" and "log", so the
placement of these files can be changed with a single statement.
-
Allow a client to request logging.
-
Allow the
LOAD DATA INFILE statement
to read files that have been compressed with gzip.
-
Fix sorting and grouping of
BLOB columns (partly solved now).
-
Change to use semaphores when counting threads. One should first implement
a semaphore library for MIT-pthreads.
-
Add full support for
JOIN with parentheses.
-
As an alternative to the one-thread-per-connection model, manage a pool
of threads to handle queries.
-
Allow
GET_LOCK() to obtain more than one lock. When doing this,
one must also handle the possible deadlocks this change will introduce.
We aim toward full compliance with SQL-92/SQL-99, so there are no features
we plan not to implement.
This section introduces you to the MySQL mailing lists and provides
some guidelines as to how the lists should be used. When you subscribe to a mailing
list, you will receive all postings to the list as email messages. You can
also 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-specialized 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 1.7.1.3 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 topics 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 topics concerning connecting to the MySQL server with ODBC.
myodbc-digest-
This is the
myodbc list in digest form.
mysqlcc-
This list is for all topics concerning the
MySQL Control Center graphical client.
mysqlcc-digest-
This is the
mysqlcc list in digest form.
plusplus-
This list is for all topics 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 topics 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 questions from a MySQL mailing list, one
option is to purchase 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.
mysql-france-subscribe@yahoogroups.com
-
A French mailing list.
list@tinc.net
-
A Korean mailing list.
Email
subscribe mysql your@email.address to this list.
mysql-de-request@lists.4t2.com
-
A German mailing list.
Email
subscribe mysql-de your@email.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.
Email
subscribe mysql-br your@email.address to this list.
mysql-alta@elistas.net
-
A Spanish mailing list.
Email
subscribe mysql your@email.address to this list.
Before posting a bug report or question, please do the following:
-
Start by searching the MySQL online manual at
http://www.mysql.com/doc/.
We try to keep the manual up to date by updating it frequently with
solutions to newly found problems. The change history appendix
(http://www.mysql.com/doc/en/News.html) can be particularly
useful since it is quite possible that a newer version already
contains a solution to your problem.
-
Search in the bugs database at http://bugs.mysql.com/ to see
whether the bug has already been reported and fixed.
-
Search the MySQL mailing list archives at
http://lists.mysql.com/.
-
You can also use http://www.mysql.com/search/ to search all the
web pages (including the manual) that are located at the MySQL AB web site.
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.
The normal place to report bugs is http://bugs.mysql.com/, which is the
address for our bugs database.
This database is public, and can be browsed and searched by anyone.
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 |
