文档目录

COLLATIONS

COLLATIONS 表提供了 CHARACTER_SETS 表中字符集对应的排序规则列表。目前 TiDB 包含该表仅为兼容 MySQL。

USE information_schema;
DESC collations;
+--------------------+-------------+------+------+---------+-------+
| Field              | Type        | Null | Key  | Default | Extra |
+--------------------+-------------+------+------+---------+-------+
| COLLATION_NAME     | varchar(32) | YES  |      | NULL    |       |
| CHARACTER_SET_NAME | varchar(32) | YES  |      | NULL    |       |
| ID                 | bigint(11)  | YES  |      | NULL    |       |
| IS_DEFAULT         | varchar(3)  | YES  |      | NULL    |       |
| IS_COMPILED        | varchar(3)  | YES  |      | NULL    |       |
| SORTLEN            | bigint(3)   | YES  |      | NULL    |       |
+--------------------+-------------+------+------+---------+-------+
6 rows in set (0.00 sec)
SELECT * FROM collations WHERE character_set_name='utf8mb4';
+----------------+--------------------+------+------------+-------------+---------+
| COLLATION_NAME | CHARACTER_SET_NAME | ID   | IS_DEFAULT | IS_COMPILED | SORTLEN |
+----------------+--------------------+------+------------+-------------+---------+
| utf8mb4_bin    | utf8mb4            |   46 | Yes        | Yes         |       1 |
+----------------+--------------------+------+------------+-------------+---------+
1 row in set (0.00 sec)

COLLATION 表中列的含义如下:

  • COLLATION_NAME:排序规则名称
  • CHARACTER_SET_NAME:排序规则所属的字符集名称
  • ID:排序规则的 ID
  • IS_DEFAULT:该排序规则是否是所属字符集的默认排序规则
  • IS_COMPILED:字符集是否编译到服务器中
  • SORTLEN:排序规则在对字符进行排序时,所分配内存的最小长度