Purpose
information_schema.KEY_COLUMN_USAGE displays information about key columns that have constraints.
Related tables/views
__all_foreign_key_column
__all_foreign_key_column_history
Fields
| Field | Type | Nullable | Description |
|---|---|---|---|
| CONSTRAINT_CATALOG | varchar(3) | NO | The name of the catalog to which the table containing the column belongs. The value of this field is fixed to def. |
| CONSTRAINT_SCHEMA | varchar(128) | NO | The name of the database. |
| CONSTRAINT_NAME | varchar(256) | NO | The name of the constraint. The value of this field is PRIMARY, the column name, or the foreign key name. |
| TABLE_CATALOG | varchar(3) | NO | The name of the catalog to which the table belongs. |
| TABLE_SCHEMA | varchar(128) | NO | The name of the database. |
| TABLE_NAME | varchar(256) | NO | The name of the table. |
| COLUMN_NAME | varchar(128) | NO | The name of the column. |
| ORDINAL_POSITION | bigint(20) | NO | The serial number of the column within the table. |
| POSITION_IN_UNIQUE_CONSTRAINT | null | NO | The value of this field is NULL for UNIQUE and PRIMARY KEY constraints. For FOREIGN KEY constraints, the value of this field is the ordinal position in the key of the table that is being referenced. |
| REFERENCED_TABLE_SCHEMA | null | NO | The name of the database referenced by the constraint. |
| REFERENCED_TABLE_NAME | null | NO | The name of the table referenced by the constraint. |
| REFERENCED_COLUMN_NAME | null | NO | The name of the column referenced by the constraint. |