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The INFORMATION_SCHEMA KEY_COLUMN_USAGE Table

The KEY_COLUMN_USAGE table describes which key columns have constraints. mysql> mysql> desc  INFORMATION_SCHEMA.KEY_COLUMN_USAGE; +-------------------------------+--------------+------+-----+---------+-------+ | Field                         | Type         | Null | Key | Default | Extra | +-------------------------------+--------------+------+-----+---------+-------+ | CONSTRAINT_CATALOG            | varchar(512) | YES  |     | NULL    |       | | CONSTRAINT_SCHEMA             | varchar(64)  | NO   |     |         |       | | CONSTRAINT_NAME               | varchar(64)  | NO   |     |         |       | | TABLE_CATALOG                 | varchar(512) | YES  |     | NULL    |       | | TABLE_SCHEMA                  | varchar(64)  | NO   |     |         |       | | TABLE_NAME                    | varchar(64)  | NO   |     |         |       | | COLUMN_NAME                   | varchar(64)  | NO   |     |         |       | | ORDINAL_POSITION              | bigint(10)   | NO   |     | 0       |       | | POSITION_IN_UNIQUE_CONSTRAINT | bigint(10)   | YES  |     | NULL    |       | | REFERENCED_TABLE_SCHEMA       | varchar(64)  | YES  |     | NULL    |       | | REFERENCED_TABLE_NAME         | varchar(64)  | YES  |     | NULL    |       | | REFERENCED_COLUMN_NAME        | varchar(64)  | YES  |     | NULL    |       | +-------------------------------+--------------+------+-----+---------+-------+ 12 rows in set (0.00 sec)