By default, mysqld produces error messages in English, but they can also be displayed in any of several other languages: Czech, Danish, Dutch, Estonian, French, German, Greek, Hungarian, Italian, Japanese, Korean, Norwegian, Norwegian-ny, Polish, Portuguese, Romanian, Russian, Slovak, Spanish, or Swedish.

You can select which language the server uses for error messages using the instructions in this section.

As of MySQL 5.5, the server searches for the error message file in two locations:

The lc_messages_dir system variable has only a global value and is read only. lc_messages has global and session values and can be modified at runtime, so the error message language can be changed while the server is running, and individual clients each can have a different error message language by changing their session lc_messages value to a different locale name. For example, if the server is using the fr_FR locale for error messages, a client can execute this statement to receive error messages in English:

mysql> SET lc_messages = 'en_US';

Before MySQL 5.5, the lc_messages_dir and lc_messages system variables were unavailable. To start mysqld with a particular language for error messages, the --language or -L option were used. The option value can be a language name or the full path to the error message file. For example:

shell> mysqld --language=french

Or:

shell> mysqld --language=/usr/local/share/french

Specify the language name in lowercase.

MySQL 5.5 treats --language as an alias for lc_messages_dir.

By default, the language files are located in the share/mysql/LANGUAGE directory under the MySQL base directory.

For information about changing the character set for error messages (rather than the language), see Section 10.1.6, “Character Set for Error Messages”.

You can change the content of the error messages produced by the server using the instructions in the MySQL Internals manual, available at MySQL Internals: Error Messages. If you do change the content of error messages, remember to repeat your changes after each upgrade to a newer version of MySQL.