DB2


- 3


SQL: .

SELECT DISTINCT ,

FROM P;

theta

, . theta- Y t, , t - , , - ,

, . theta b. Y . . B.Y , theta .

SQL:

SELECT S.*, P.*

FROM S, P

WHERE S. > . ;

theta , . , . , , . .

, , () () (). Y, Y. A.Y B.Y . X, , . . (,)

, .

SQL:

SELECT DISTINCT _ FROM SP, SP1

WHERE NOT EXISTS

(SELECT _ FROM P

WHERE NOT EXISTS

(SELECT * FROM SP, SP2

WHERE SP2. _ =

SP1 ._

AND SP2. _ = ._));

, : ) SP , _ _ ( ) ) _ ( , , , ). ; _, , .




- -  - -  - -