MySQL 8.0 Reference Manual Including MySQL NDB Cluster 8.0
For applications that store data using the default MySQL character
set and collation (utf8mb4
,
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 sjis
.
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
utf8mb4
and
utf8mb4_0900_ai_ci
.
Specify character settings per database.
To create a database such that its tables use a given
default character set and collation for data storage, use a
CREATE DATABASE
statement
like this:
CREATE DATABASE mydb CHARACTER SET latin1 COLLATE latin1_swedish_ci;
Tables created in the database use latin1
and latin1_swedish_ci
by 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=latin1
command-line option to achieve the same effect as SET
NAMES 'latin1'
.
For more information about configuring client connections, see Section 12.4, “Connection Character Sets and Collations”.
If you use ALTER DATABASE
to
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 15.1.17, “CREATE PROCEDURE and CREATE FUNCTION Statements”.)
Specify character settings at server startup.
To select a character set and collation at server startup,
use the
--character-set-server
and
--collation-server
options.
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 NAMES
or
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
NAMES
to be executed automatically for each client
that connects. However, this may yield inconsistent results
because the init_connect
value is not executed for users who have the
CONNECTION_ADMIN
privilege (or
the deprecated SUPER
privilege).
Specify character settings at MySQL configuration time.
To select a character set and collation if you configure and
build MySQL from source, use the
DEFAULT_CHARSET
and
DEFAULT_COLLATION
CMake options:
cmake . -DDEFAULT_CHARSET=latin1 \ -DDEFAULT_COLLATION=latin1_swedish_ci
The resulting server uses latin1
and
latin1_swedish_ci
as the default for
databases and tables and for client connections. It is
unnecessary to use
--character-set-server
and
--collation-server
to specify
those defaults at server startup. It is also unnecessary for
applications to configure their connection using
SET NAMES
or 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 intend to
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
this <meta>
tag within your
<head>
element:
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />