Each collation must have a unique ID. To add a collation, you must choose an ID value that is not currently used. MySQL supports two-byte collation IDs. The range of IDs from 1024 to 2047 is reserved for user-defined collations.
The collation ID that you choose appears in these contexts:
The
ID
column of the Information SchemaCOLLATIONS
table.The
Id
column ofSHOW COLLATION
output.The
charsetnr
member of theMYSQL_FIELD
C API data structure.The
number
member of theMY_CHARSET_INFO
data structure returned by themysql_get_character_set_info()
C API function.
To determine the largest currently used ID, issue the following statement:
Press CTRL+C to copymysql> SELECT MAX(ID) FROM INFORMATION_SCHEMA.COLLATIONS; +---------+ | MAX(ID) | +---------+ | 247 | +---------+
To display a list of all currently used IDs, issue this statement:
Press CTRL+C to copymysql> SELECT ID FROM INFORMATION_SCHEMA.COLLATIONS ORDER BY ID; +-----+ | ID | +-----+ | 1 | | 2 | | ... | | 52 | | 53 | | 57 | | 58 | | ... | | 98 | | 99 | | 128 | | 129 | | ... | | 247 | +-----+
Before upgrading, you should save the configuration files that you change. If you upgrade in place, the process replaces the modified files.