## 37.18. `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 37.16. `constraint_column_usage` Columns**

|                                                                       Column Type<br/><br/> Description                                                                      |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|`table_catalog` `sql_identifier`<br/><br/> 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`<br/><br/> Name of the schema that contains the table that contains the column that is used by some constraint                 |
|                              `table_name` `sql_identifier`<br/><br/> Name of the table that contains the column that is used by some constraint                              |
|                                         `column_name` `sql_identifier`<br/><br/> Name of the column that is used by some constraint                                          |
|                       `constraint_catalog` `sql_identifier`<br/><br/> Name of the database that contains the constraint (always the current database)                        |
|                                        `constraint_schema` `sql_identifier`<br/><br/> Name of the schema that contains the constraint                                        |
|                                                     `constraint_name` `sql_identifier`<br/><br/> Name of the constraint                                                      |

