collation_character_set_applicability

collation_character_set_applicability视图指示哪种字符集适用于哪种排序规则。这个视图为只读，不允许修改。所有用户对这个视图有“读取”权限。

表1 information_schema.collation_character_set_applicability字段
名称	类型	描述
COLLATION_NAME	varchar(32)	排序规则名称。
CHARACTER_SET_NAME	varchar(32)	与排序规则关联的字符集的名称。

GUC参数m_format_dev_version控制行为保持前向兼容，m_format_dev_version取值为s2时，可使用最新功能，其他取值保持前向兼容。

m_format_dev_version取值不为s2时，视图仅展示当前数据库的字符集相关的字符集排序规则信息：

m_db=# SET m_format_dev_version=s1;
SET
m_db=# SELECT * FROM information_schema.collation_character_set_applicability;
   COLLATION_NAME   | CHARACTER_SET_NAME
--------------------+--------------------
 utf8mb4_0900_ai_ci | UTF8
 utf8_bin           | UTF8
 utf8_unicode_ci    | UTF8
 utf8_general_ci    | UTF8
 utf8mb4_bin        | UTF8
 utf8mb4_unicode_ci | UTF8
 utf8mb4_general_ci | UTF8
 POSIX              | UTF8
 C                  | UTF8
 default            | UTF8
(10 rows)

m_format_dev_version取值为s2时，视图可以查询所有可用排序规则和字符集的对应关系：

m_db=# SET m_format_dev_version=s2;
SET
m_db=# SELECT * FROM  information_schema.collation_character_set_applicability;
   COLLATION_NAME   | CHARACTER_SET_NAME
--------------------+--------------------
 binary             | binary
 gbk_chinese_ci     | gbk
 gbk_bin            | gbk
 utf8mb4_general_ci | utf8mb4
 utf8mb4_unicode_ci | utf8mb4
 utf8mb4_bin        | utf8mb4
 utf8_general_ci    | utf8
 utf8_unicode_ci    | utf8
 utf8_bin           | utf8
 utf8mb4_0900_ai_ci | utf8mb4
 gb18030_chinese_ci | gb18030
 gb18030_bin        | gb18030
 latin1_swedish_ci  | latin1
 latin1_bin         | latin1
(14 rows)