The TABLE_CONSTRAINTS_EXTENSIONS
      table provides information about table constraint attributes
      defined for primary and secondary storage engines.
        The TABLE_CONSTRAINTS_EXTENSIONS
        table is reserved for future use.
      The TABLE_CONSTRAINTS_EXTENSIONS
      table has these columns:
- CONSTRAINT_CATALOG- The name of the catalog to which the table belongs. 
- CONSTRAINT_SCHEMA- The name of the schema (database) to which the table belongs. 
- CONSTRAINT_NAME- The name of the constraint. 
- TABLE_NAME- The name of the table. 
- ENGINE_ATTRIBUTE- Constraint attributes defined for the primary storage engine. Reserved for future use. 
- SECONDARY_ENGINE_ATTRIBUTE- Constraint attributes defined for the secondary storage engine. Reserved for future use.