## 31.18. `key_column_usage`

The view `key_column_usage` identifies all columns in the current database that are restricted by some unique, primary key, or foreign key constraint. Check constraints are not included in this view. Only those columns are shown that are contained in a table owned by the current user.

Table 31.16. `key_column_usage` Columns

Name | Data Type | Description
--- | --- | ---
`constraint_catalog` | `sql_identifier` | Name of the database that contains the constraint (always the current database)
`constraint_schema` | `sql_identifier` | Name of the schema that contains the constraint
`constraint_name` | `sql_identifier` | Name of the constraint
`table_catalog` | `sql_identifier` | Name of the database that contains the table that contains the column that is restricted by some constraint (always the current database)
`table_schema` | `sql_identifier` | Name of the schema that contains the table that contains the column that is restricted by some constraint
`table_name` | `sql_identifier` | Name of the table that contains the column that is restricted by some constraint
`column_name` | `sql_identifier` | Name of the column that is restricted by some constraint
`ordinal_position` | `cardinal_number` | Ordinal position of the column within the constraint key (count starts at 1)