Yurttas/PL/DBL/postgres/F/01/PC/q11.sql

 1/*
 2REM
 3REM q11.sql
 4REM
 5REM Find the average hard disk size of a PC for all those
 6REM manufacturers that make printers.
 7REM
 8*/
 9
10SELECT current_schema();
11SET search_path to "pc";
12
13SELECT P.maker, AVG(hd)
14FROM Product P, PC
15WHERE P.model=PC.model
16  AND P.maker IN (SELECT P.maker
17                  FROM Product P, Printer R
18                  WHERE P.model=R.model)
19GROUP BY P.maker;