# 36.18. constraint\_column\_usage

The view `constraint_column_usage` identifies all columns in the current database that are used by some constraint. Only those columns are shown that are contained in a table owned by a currently enabled role. For a check constraint, this view identifies the columns that are used in the check expression. For a foreign key constraint, this view identifies the columns that the foreign key references. For a unique or primary key constraint, this view identifies the constrained columns.

#### **Table 36.16. `constraint_column_usage` Columns**

| Name                 | Data Type        | Description                                                                                                                         |
| -------------------- | ---------------- | ----------------------------------------------------------------------------------------------------------------------------------- |
| `table_catalog`      | `sql_identifier` | Name of the database that contains the table that contains the column that is used 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 used by some constraint                                 |
| `table_name`         | `sql_identifier` | Name of the table that contains the column that is used by some constraint                                                          |
| `column_name`        | `sql_identifier` | Name of the column that is used by some constraint                                                                                  |
| `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                                                                                                              |