Order By in Sub Query

Question

Hi All,
I am trying to following SQL
select d.deptno,
d.dname,
e.empno,
e.ename,
e.sal
from dept d,
emp e
where d.deptno = e.deptno
and (e.empno, e.sal) in ( select e2.empno, e2.sal
from emp e2
where e2.deptno = d.deptno
and rownum < 3
order by e2.sal desc)
order by d.deptno, e.sal desc
This works fine if I remove the order by clause in the subquery.
In case the order by clause is still there it give me a error
or "invalid relational operator" on the order by clause in the
subquery. WHY !!!!!!
Thanks
Monish

Answer 1

The version of Oracle you are using may or may not be part of
your problem. The syntax is not valid in any version.
If you are using a newer version, you can try re-writing it like
this:
SELECT   deptno, dname, empno, ename, sal
FROM     (SELECT d.deptno, d.dname,
                 e.empno, e.ename, e.sal,
                 RANK () OVER
                      (PARTITION BY d.deptno
                       ORDER BY e.sal DESC) rk
          FROM   dept d, emp e
          WHERE  d.deptno = e.deptno)
WHERE    rk < 3
ORDER BY deptno, sal DESC;
    DEPTNO DNAME               EMPNO ENAME             SAL
        10 ACCOUNTING           7839 KING             5000
        10 ACCOUNTING           7782 CLARK            2450
        20 RESEARCH             7788 SCOTT            3000
        20 RESEARCH             7902 FORD             3000
        30 SALES                7698 BLAKE            2850
        30 SALES                7499 ALLEN            1600
6 rows selected.
If you are using an older version, you can try re-writing it
like this:
SELECT  d.deptno, d.dname,
        e.empno, e.ename, e.sal
FROM    dept d, emp e
WHERE   d.deptno = e.deptno
AND     3 >
        (SELECT COUNT (*) + 1
         FROM   dept d2, emp e2
         WHERE  d2.deptno = e2.deptno
         AND    d2.deptno = d.deptno
         AND    e2.sal > e.sal)
ORDER BY d.deptno, e.sal DESC;The second solution will produce the same results as the first
and will work in newer versions as well, but will run
significantly slower on large tables.