DB2



              

: - 2


, :

CREATE TABLE SP /* S */

PRIMARY KEY (_, _)

FOREIGN KEY (_ IDENTIFIES S

NULLS NOT ALLOWED

DELETE OF S.RESTRICTED

UPDATE OF S. _

CASCADES)

FOREIGN KEY (_ IDENTIFIES P

NULLS NOT ALLOWED

DELETE OF P.RESTRICTED

UPDATE OF P._

RESTRICTED)

FIELDS (_ . . ., _ . .

., . . .);

PRIMARY KEY ( ) FOREIGN KEY ( ) :

-PRIMARY-KEY

:: = PRIMARY KEY (),

-, _, -, , (_, _).

-FOREIGN-KEY

: : = FOREIGN KEY ( IDENTIFIES

NULLS [NOT] ALLOWED

DELETE OF

UPDATE OF ),

) , -, . . -, -, ; ) -; ) -- - , , ) CASCADES (), RESTRICTED () NULLIFIES ( ).

. PRIMARY KEY FOREIGN KEY, , DB2.