mysql 5 的 charset

除了 server,database,table,column可以特定的指定字符集及校對排序規則外，還有connect,client，不過connect,client我就沒去太看他，保持client和server的相同才可簡化問題。

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10.3.1. Server Character Set and Collation
The current server character set and collation are available as the values of the character_set_server and collation_server system variables. These variables can be changed at runtime.

10.3.2. Database Character Set and Collation
The database character set and collation are used as default values if the table character set and collation are not specified in CREATE TABLE statements. They have no other purpose.

The character set and collation for the default database are available as 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 variables, character_set_server and collation_server.

10.3.3. Table Character Set and Collation
MySQL chooses the table character set and collation thus:

If both CHARACTER SET X and COLLATE Y were specified, then character set X and collation Y.

If CHARACTER SET X was specified without COLLATE, then character set X and its default collation.

Otherwise, the database character set and collation.

The table character set and collation are used as default values if the column character set and collation are not specified in individual column definitions. The table character set and collation are MySQL extensions; there are no such things in standard SQL.

10.3.4. Column Character Set and Collation
MySQL chooses the column character set and collation thus:

If both CHARACTER SET X and COLLATE Y were specified, then character set X and collation Y.

If CHARACTER SET X was specified without COLLATE, then character set X and its default collation.

Otherwise, the table character set and collation.

The CHARACTER SET and COLLATE clauses are standard SQL.