table_constraints
   The view table_constraints contains all
   constraints belonging to tables that the current user owns or has
   some privilege other than SELECT on.
  
Table 36.49. table_constraints 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 (always the current database) | 
| table_schema | sql_identifier | Name of the schema that contains the table | 
| table_name | sql_identifier | Name of the table | 
| constraint_type | character_data | Type of the constraint: CHECK,FOREIGN KEY,PRIMARY KEY,
       orUNIQUE | 
| is_deferrable | yes_or_no | YESif the constraint is deferrable,NOif not | 
| initially_deferred | yes_or_no | YESif the constraint is deferrable and initially deferred,NOif not | 
| enforced | yes_or_no | Applies to a feature not available in
      PostgreSQL (currently always YES) |