sql> select deptno, ename,
2         row_number () over (partition by deptno order by sal desc) seq
3    from emp;

    deptno ename             seq
---------- ---------- ----------
        10 king                1
        10 clark               2
        10 miller              3
        20 scott               1
        20 ford                2
        20 jones               3
        20 adams               4
        20 smith               5
        30 blake               1
        30 allen               2
        30 turner              3
        30 ward                4
        30 martin              5
        30 james               6

14 rows selected.

sql> select deptno,
  2  max(decode(seq,1,ename,null)) highest,
  3  max(decode(seq,2,ename,null)) second,
  4  max(decode(seq,3,ename,null)) third
  5  from (
  6  select deptno,ename,
  7  row_number() over
  8  (partition by deptno order by sal desc) seq
  9  from emp)
 10  where seq <=3 group by deptno
 11  /

deptno highest    second     third
---------- ---------- ---------- ----------
10 king       clark      miller
20 scott      ford       jones
30 blake      allen      turner