Question

I have a table with the following values (Please ignore index, here column with R1..R10 being the PK of the table.

1   R1  M1  Mo1
2   R2  M2  Mo3
3   R3  M4  Mo6
4   R4  M2  Mo1
5   R5  M7  Mo1
6   R6  M5  Mo2
7   R7  M6  Mo1
8   R8  M4  Mo4
9   R9  M9  Mo3
10  R10 M3  Mo9

I want to find a value of Mo[i] for which number of R[i] are max. For example in above case Mo1 has maximum number of R[i] values so it must return Mo1.

I have been doing the stuff using count, but not succeeded yet.

Here is what i wrote

select Mo from table1 where Mo=(select max(r.Mo),max(count((r.Mo))) from table1 )r group by r.Mo

Answer 1

Try this:

select Mo from
(
    select Mo from 
    (
        select Mo, count(*) cnt
        from table1
        group by Mo
    )
    order by cnt desc
) where rownum = 1;

This first groups the table by the column Mo, resulting in

Mo  | cnt
----+----
Mo3 | 2
Mo2 | 1
Mo4 | 1
Mo1 | 4
Mo6 | 1
Mo9 | 1

It then orders this by the count which results in this:

Mo 
---
Mo1
Mo3
Mo6
Mo2
Mo4
Mo9

And then it simply returns the first row of the result which results in Mo1.