Eliminate Data based on a column

Question

Hello All,
I am in very weird situation. I have to filter data based on a column. For example, my data is like :
Col1       Col2        Col3       Col4
A1         A              B           C
A2         A              B            D
A3         A              B            E
F           G              H             I
J            K               L             M
I have to filter data based on col1 which has the maximum if Col2 and Col3 have same value. So the o/p of above data will be  if (A3> A2 > A1) as  Col2 and Col3 have same value A and B:
Col1       Col2            Col3       Col4
A3             A              B            E
F              G               H             I
J               K               L             M
Please suggest.

Answer 1

Hi,
One way to do that is a Top-N Query .  Since you didn't post your table, I'll use scott.emp to illustrate.  Ename, deptno, job and hiredate in scott.emp correspond to col1, col2, col3 and co4l (respectively) in your table.
WITH got_r_num AS
SELECT ename, deptno, job, hiredate
, ROW_NUMBER () OVER ( PARTITION BY  deptno, job
               ORDER BY      ename   DESC
       ) AS r_num
FROM scott.emp
SELECT ename, deptno, job, hiredate
FROM got_r_num
WHERE r_num  = 1
The query above displays only 1 row for each distinct combination of deptno and job, the row with the last ename.