Every database has a database character set and a database
collation. The CREATE DATABASE
and ALTER DATABASE statements
have optional clauses for specifying the database character
set and collation:
CREATE DATABASEdb_name[[DEFAULT] CHARACTER SETcharset_name] [[DEFAULT] COLLATEcollation_name] ALTER DATABASEdb_name[[DEFAULT] CHARACTER SETcharset_name] [[DEFAULT] COLLATEcollation_name]
The keyword SCHEMA can be used instead of
DATABASE.
All database options are stored in a text file named
db.opt that can be found in the database
directory.
The CHARACTER SET and
COLLATE clauses make it possible to create
databases with different character sets and collations on the
same MySQL server.
Example:
CREATE DATABASE db_name CHARACTER SET latin1 COLLATE latin1_swedish_ci;
MySQL chooses the database character set and database collation in the following manner:
If both
CHARACTER SETandXCOLLATEare specified, character setYXand collationYare used.If
CHARACTER SETis specified withoutXCOLLATE, character setXand its default collation are used. To see the default collation for each character set, use theSHOW COLLATIONstatement.If
COLLATEis specified withoutYCHARACTER SET, the character set associated withYand collationYare used.Otherwise, the server character set and server collation are used.
The character set and collation for the default database can
be determined from the values of the
character_set_database and
collation_database system
variables. The server sets these variables whenever the
default database changes. If there is no default database, the
variables have the same value as the corresponding
server-level system variables,
character_set_server and
collation_server.
To see the default character set and collation for a given database, use these statements:
USE db_name;
SELECT @@character_set_database, @@collation_database;
Alternatively, to display the values without changing the default database:
SELECT DEFAULT_CHARACTER_SET_NAME, DEFAULT_COLLATION_NAME
FROM INFORMATION_SCHEMA.SCHEMATA WHERE SCHEMA_NAME = 'db_name';
The database character set and collation affect these aspects of server operation:
For
CREATE TABLEstatements, the database character set and collation are used as default values for table definitions if the table character set and collation are not specified. To override this, provide explicitCHARACTER SETandCOLLATEtable options.For
LOAD DATAstatements that include noCHARACTER SETclause, the server uses the character set indicated by thecharacter_set_databasesystem variable to interpret the information in the file. To override this, provide an explicitCHARACTER SETclause.For stored routines (procedures and functions), the database character set and collation in effect at routine creation time are used as the character set and collation of character data parameters for which the declaration includes no
CHARACTER SETorCOLLATEattribute. To override this, provide explicitCHARACTER SETandCOLLATEattributes.