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,
       or UNIQUE
       | 
is_deferrable | yes_or_no | YES if the constraint is deferrable, NO if not | 
initially_deferred | yes_or_no | YES if the constraint is deferrable and initially deferred, NO if not | 
enforced | yes_or_no | Applies to a feature not available in
      PostgreSQL (currently always
      YES) |