Posted by Are you stuck with a database that does not offer analytic SQL facilities ? Never mind, you can use the following trivial 
query can determine the median salary from the EMP table
SQL> select avg(sal) from
2 ( select x.sal
3 from scott.EMP x, scott.EMP y
4 group by x.sal
5 having sum(sign(1-sign(y.sal-x.sal))) in
6 ( trunc((count(*)+1)/2), trunc((count(*)+2)/2) ) );
AVG(SAL)
----------
1550
Of course, if that is basically gobbledygook to you (and it certainly is to me!)…well, you should check out Oracle’s cool Analytic SQL features here
Learning is not a spectator sport 
That doesn’t seem to work (reliably) if you have duplicate values–if you have one or more people with the same salary. Sometimes I get nulls, and sometimes I get a value that’s off.
It does appear to work on SCOTT.EMP as shipped by Oracle, but it returns null if you restrict it to SAL < 2000.
Try this on for size:
WITH q AS (SELECT * FROM scott.emp /* WHERE sal < 2000 */)
SELECT avg(max(x.sal))
FROM q x, q y
GROUP BY x.rowid
HAVING count(CASE
WHEN x.sal < y.sal THEN 1
WHEN x.sal = y.sal AND x.rowid < y.rowid THEN 1
END)
BETWEEN count(*)/2 – 1 AND count(*)/2
And if you wanted something a little more vaguely understandable (but what’s the fun in that?…):
WITH q AS (SELECT * FROM scott.emp /* WHERE sal < 2000 */)
SELECT avg(x.sal)
FROM q x
WHERE (
SELECT count(*)
FROM q y
WHERE x.sal < y.sal
OR x.sal = y.sal
AND x.rowid < y.rowid
) BETWEEN (SELECT count(*)/2-1 FROM q) AND (SELECT count(*)/2 FROM q)