{ ADD { out_of_line_constraint
        [ out_of_line_constraint ]...
      | out_of_line_REF_constraint
      }
| MODIFY { CONSTRAINT constraint
         | PRIMARY KEY
         | UNIQUE (column)
           [, UNIQUE (column) ]...
         }
            constraint_state
| RENAME CONSTRAINT old_name TO new_name
| drop_constraint_clause
}