12.14.2 选择排序规则 ID
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:
mysql> SELECT MAX(ID) FROM INFORMATION_SCHEMA.COLLATIONS;
+---------+
| MAX(ID) |
+---------+
| 247 |
+---------+
To display a list of all currently used IDs, issue this statement:
mysql> 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.