<p>I want to find 2<sup>nd</sup>, 3<sup>rd</sup>, ... n<sup>th</sup> maximum value of a column.</p>

You could sort the column into descending format and then just obtain the value from the nth row.
EDIT::
Updated as per comment request.
WARNING
completely untested!
```
```
SELECT DOB FROM (SELECT DOB FROM USERS ORDER BY DOB DESC) WHERE ROWID = 6
```
```
Something like the above should work for Oracle ... you might have to get the syntax right first!