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 |
| utf8mb4_general_ci | utf8mb4 | 45 | | Yes | 1 |
| utf8mb4_unicode_ci | utf8mb4 | 224 | | Yes | 1 |
+--------------------+--------------------+------+------------+-------------+---------+
3 rows in set (0.001 sec)
COLLATIONS 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 IDIS_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