Hi

As per my understanding if a table is like below

ColA         ColB

------------------

1                 2

2                 3

3                 4

4                 5

                   6

Then the result Should be like below

ColA         ColB

------------------

2                 3

3                 4

4                 5

If this is what is expected then the query should be lik

select * from table where colB in (select colA from table where colA is not null)

Hope this helps.

Thanks.