37.18. constraint_table_usage
  The view
  
   constraint_table_usage
  
  identifies all
   tables in the current database that are used by some constraint and
   are owned by a currently enabled role.  (This is different from the
   view
  
   table_constraints
  
  , which identifies all
   table constraints along with the table they are defined on.)  For a
   foreign key constraint, this view identifies the table that the
   foreign key references.  For a unique or primary key constraint,
   this view simply identifies the table the constraint belongs to.
   Check constraints and not-null constraints are not included in this
   view.
 
   
    Table 37.16. 
    
     constraint_table_usage
    
    Columns
   
  
| Name | Data Type | Description | 
|---|---|---|
| 
        table_catalog
        | 
        sql_identifier
        | Name of the database that contains the table that is used by some constraint (always the current database) | 
| 
        table_schema
        | 
        sql_identifier
        | Name of the schema that contains the table that is used by some constraint | 
| 
        table_name
        | 
        sql_identifier
        | Name of the table 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 |