For applications that store data using the default MySQL character
set and collation (
utf8mb4_0900_ai_ci), no special configuration
should be needed. If applications require data storage using a
different character set or collation, you can configure character
set information several ways:
Specify character settings per database. For example, applications that use one database might use the default of
utf8mb4, whereas applications that use another database might use
Specify character settings at server startup. This causes the server to use the given settings for all applications that do not make other arrangements.
Specify character settings at configuration time, if you build MySQL from source. This causes the server to use the given settings as the defaults for all applications, without having to specify them at server startup.
When different applications require different character settings, the per-database technique provides a good deal of flexibility. If most or all applications use the same character set, specifying character settings at server startup or configuration time may be most convenient.
For the per-database or server-startup techniques, the settings control the character set for data storage. Applications must also tell the server which character set to use for client/server communications, as described in the following instructions.
The examples shown here assume use of the
latin1 character set and
latin1_swedish_ci collation in particular
contexts as an alternative to the defaults of
Specify character settings per database. To create a database such that its tables will use a given default character set and collation for data storage, use a
CREATE DATABASEstatement like this:
CREATE DATABASE mydb CHARACTER SET latin1 COLLATE latin1_swedish_ci;
Tables created in the database will use
latin1_swedish_ciby default for any character columns.
Applications that use the database should also configure their connection to the server each time they connect. This can be done by executing a
SET NAMES 'latin1'statement after connecting. The statement can be used regardless of connection method (the mysql client, PHP scripts, and so forth).
In some cases, it may be possible to configure the connection to use the desired character set some other way. For example, to connect using mysql, you can specify the
--default-character-set=latin1command-line option to achieve the same effect as
SET NAMES 'latin1'.
For more information about configuring client connections, see Section 10.4, “Connection Character Sets and Collations”.Note
If you use
ALTER DATABASEto change the database default character set or collation, existing stored routines in the database that use those defaults must be dropped and recreated so that they use the new defaults. (In a stored routine, variables with character data types use the database defaults if the character set or collation are not specified explicitly. See Section 13.1.17, “CREATE PROCEDURE and CREATE FUNCTION Syntax”.)
Specify character settings at server startup. To select a character set and collation at server startup, use the
--collation-serveroptions. For example, to specify the options in an option file, include these lines:
[mysqld] character-set-server=latin1 collation-server=latin1_swedish_ci
These settings apply server-wide and apply as the defaults for databases created by any application, and for tables created in those databases.
It is still necessary for applications to configure their connection using
SET NAMESor equivalent after they connect, as described previously. You might be tempted to start the server with the
--init_connect="SET NAMES 'latin1'"option to cause
SET NAMESto be executed automatically for each client that connects. However, this may yield inconsistent results because the
init_connectvalue is not executed for users who have the
Specify character settings at MySQL configuration time. To select a character set and collation if you configure and build MySQL from source, use the
cmake . -DDEFAULT_CHARSET=latin1 \ -DDEFAULT_COLLATION=latin1_swedish_ci
The resulting server uses
latin1_swedish_cias the default for databases and tables and for client connections. It is unnecessary to use
--collation-serverto specify those defaults at server startup. It is also unnecessary for applications to configure their connection using
SET NAMESor equivalent after they connect to the server.
Regardless of how you configure the MySQL character set for
application use, you must also consider the environment within
which those applications execute. For example, if you will send
statements using UTF-8 text taken from a file that you create in
an editor, you should edit the file with the locale of your
environment set to UTF-8 so that the file encoding is correct and
so that the operating system handles it correctly. If you use the
mysql client from within a terminal window, the
window must be configured to use UTF-8 or characters may not
display properly. For a script that executes in a Web environment,
the script must handle character encoding properly for its
interaction with the MySQL server, and it must generate pages that
correctly indicate the encoding so that browsers know how to
display the content of the pages. For example, you can include
<meta> tag within your
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />