MySQL 9.3 Reference Manual Including MySQL NDB Cluster 9.3
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
.
The CHARACTER SET
and
COLLATE
clauses make it possible to create
databases with different character sets and collations on the
same MySQL server.
Database options are stored in the data dictionary and can be
examined by checking the Information Schema
SCHEMATA
table.
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 SET
and
charset_name
COLLATE
are
specified, character set
collation_name
charset_name
and collation
collation_name
are used.
If CHARACTER SET
is
specified without charset_name
COLLATE
, character set
charset_name
and its default
collation are used. To see the default collation for each
character set, use the SHOW CHARACTER
SET
statement or query the
INFORMATION_SCHEMA
CHARACTER_SETS
table.
If COLLATE
is
specified without collation_name
CHARACTER SET
, the
character set associated with
collation_name
and collation
collation_name
are used.
Otherwise (neither CHARACTER SET
nor
COLLATE
is specified), 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 TABLE
statements,
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
explicit CHARACTER SET
and
COLLATE
table options.
For LOAD DATA
statements that
include no CHARACTER SET
clause, the
server uses the character set indicated by the
character_set_database
system variable to interpret the information in the file. To
override this, provide an explicit CHARACTER
SET
clause.
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 SET
or a
COLLATE
attribute. To override this,
provide CHARACTER SET
and
COLLATE
explicitly.