Yurttas/PL/DBL/oracle/F/01/PC/q05.sql

 1REM
 2REM q05.sql
 3REM
 4REM Find those manufacturers that sell Laptops, but not PC's.
 5REM
 6
 7(SELECT P.maker
 8 FROM Product P, Laptop L
 9 WHERE P.model=L.model)
10MINUS
11(SELECT P.maker
12 FROM Product P, PC
13 WHERE P.model=PC.model);