Yurttas/PL/DBL/oracle/F/01/SPJ/q04.sql

 1REM
 2REM q04.sql
 3REM
 4REM Get supplier numbers for suppliers who supply
 5REM the same part to all projects.
 6REM
 7
 8SELECT S.sn
 9FROM Suppliers S
10WHERE EXISTS 
11        (SELECT *
12         FROM Parts P
13         WHERE NOT EXISTS 
14                     (SELECT *
15                      FROM Projects J
16                      WHERE NOT EXISTS 
17                                  (SELECT *
18                                   FROM Shipments SPJ
19                                   WHERE SPJ.sn = S.sn
20                                     AND SPJ.pn = P.pn
21                                     AND SPJ.jn = J.jn)));