, , . snum "WHERE city = London" "WHERE sname = Motika", . , .
( , 4), , , . , , , .
, ( ), , , . , , : ( 5 ).
, - :
SELECT *
FROM Orders
WHERE snum = (SELECT snum
FROM Salespeople
WHERE city = 'Barcelona');
Barcelona Rifkin, snum , , . . SQL , Barcelona , , .
DISTINCT
DISTINCT, . , , Hoffman (cnum = 2001). , ( 10.2):
SELECT *
FROM Orders
WHERE snum = (SELECT DISTINCT snum
FROM Orders
WHERE cnum = 2001);
=============== SQL Execution Log ==============
| SELECT * |
| FROM Orders |
| WHERE snum = |
| (SELECT DISTINCT snum |
| FROM Orders |
| Where cnum = 2001); |
| =============================================== |
| onum amt odate cnum snum |
| ----- --------- --------- ------ ------- |
| 3003 767.19 10/03/1990 2001 1001 |
| 3008 4723.00 10/05/1990 2006 1001 |
| 3011 9891.88 10/06/1990 2006 1001 |
=================================================
10.2. DISTINCT .
, snum Hoffman 1001, snum ( , Hoffman ). , , cnum snum. , , ( ) snum cnum. DISTINCT . , .
, , . cnum ( . 19) , , . , . , (SQL , , , - ; 22).
, , , , , , , . , .