COLLATIONS
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T
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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 | YES | | NULL | |
| IS_DEFAULT | varchar(3) | YES | | NULL | |
| IS_COMPILED | varchar(3) | YES | | NULL | |
| SORTLEN | bigint | YES | | NULL | |
| PAD_ATTRIBUTE | varchar(9) | YES | | NULL | |
+--------------------+-------------+------+------+---------+-------+
7 rows in set (0.001 sec)
SELECT * FROM collations WHERE character_set_name='utf8mb4';
+--------------------+--------------------+------+------------+-------------+---------+---------------+
| COLLATION_NAME | CHARACTER_SET_NAME | ID | IS_DEFAULT | IS_COMPILED | SORTLEN | PAD_ATTRIBUTE |
+--------------------+--------------------+------+------------+-------------+---------+---------------+
| utf8mb4_0900_ai_ci | utf8mb4 | 255 | | Yes | 0 | NO PAD |
| utf8mb4_0900_bin | utf8mb4 | 309 | | Yes | 1 | NO PAD |
| utf8mb4_bin | utf8mb4 | 46 | Yes | Yes | 1 | PAD SPACE |
| utf8mb4_general_ci | utf8mb4 | 45 | | Yes | 1 | PAD SPACE |
| utf8mb4_unicode_ci | utf8mb4 | 224 | | Yes | 8 | PAD SPACE |
+--------------------+--------------------+------+------------+-------------+---------+---------------+
5 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 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。PAD_ATTRIBUTE
:在比较字符串时是否忽略末尾空格。PAD SPACE
表示忽略末尾空格(例如'abc'
等于'abc '
),而NO PAD
表示末尾空格会影响比较结果(例如'abc'
不等于'abc '
)。