Description of the illustration constraint_clauses.eps

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