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MySQL Globalization  /  Character Sets, Collations, Unicode  /  Character Set Configuration

1.14 Character Set Configuration

The MySQL server has a compiled-in default character set and collation. To change these defaults, use the --character-set-server and --collation-server options when you start the server. See Server Command Options. The collation must be a legal collation for the default character set. To determine which collations are available for each character set, use the SHOW COLLATION statement or query the INFORMATION_SCHEMA COLLATIONS table.

If you try to use a character set that is not compiled into your binary, you might run into the following problems:

  • If your program uses an incorrect path to determine where the character sets are stored (which is typically the share/mysql/charsets or share/charsets directory under the MySQL installation directory), this can be fixed by using the --character-sets-dir option when you run the program. For example, to specify a directory to be used by MySQL client programs, list it in the [client] group of your option file. The examples given here show what the setting might look like for Unix or Windows, respectively:

    [client]
    character-sets-dir=/usr/local/mysql/share/mysql/charsets
    [client]
    character-sets-dir="C:/Program Files/MySQL/MySQL Server 5.7/share/charsets"
  • If the character set is a complex character set that cannot be loaded dynamically, you must recompile the program with support for the character set.

    For Unicode character sets, you can define collations without recompiling by using LDML notation. See Section 1.13.4, “Adding a UCA Collation to a Unicode Character Set”.

  • If the character set is a dynamic character set, but you do not have a configuration file for it, you should install the configuration file for the character set from a new MySQL distribution.

  • If your character set index file (Index.xml) does not contain the name for the character set, your program displays an error message:

    Character set 'charset_name' is not a compiled character set and is not
    specified in the '/usr/share/mysql/charsets/Index.xml' file

    To solve this problem, you should either get a new index file or manually add the name of any missing character sets to the current file.

You can force client programs to use specific character set as follows:

[client]
default-character-set=charset_name

This is normally unnecessary. However, when character_set_system differs from character_set_server or character_set_client, and you input characters manually (as database object identifiers, column values, or both), these may be displayed incorrectly in output from the client or the output itself may be formatted incorrectly. In such cases, starting the mysql client with --default-character-set=system_character_set—that is, setting the client character set to match the system character set—should fix the problem.


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