collation_character_set_applicability

The collation_character_set_applicability view indicates what character set is applicable for what collation. This view is read-only. All users have the read permission on this view.

**Table 1** information_schema.collation_character_set_applicability columns
Name	Type	Description
COLLATION_NAME	varchar(32)	Name of the collation.
CHARACTER_SET_NAME	varchar(32)	Name of the character set with which the collation is associated.

The control behavior of the GUC parameter m_format_dev_version is forward compatible. When m_format_dev_version is set to s2, the latest function can be used. When m_format_dev_version is set to other values, forward compatibility is retained.

If the value of m_format_dev_version is not s2, the view displays only the character set sorting rules related to the character set of the current database.

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)

If the value of m_format_dev_version is s2, the view can query the mapping between all available collations and character sets.

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)

When m_format_dev_version is set to s2, the query result does not contain C, POSIX, or default.
The utf8 and utf8mb4 are the same character set in the M-compatible database. Therefore, collations of utf8 and utf8mb4 are equivalent to each other.