Question

How can I select the maximum row from a table? What does maximum mean — well my table has two timestamp columns, TIME1 and TIME2. The maximum column is the one with the latest value for TIME1. If that is not a unique row, then the maximum is the one within those rows with the latest value for TIME2.

This is on Oracle if that matters.

Answer 1

What you need is a “Top-N” query:

select * from (
select * from table
order by time1 desc, time2 desc
) where rownum < 2;

if you properly index on time1, time2 it will be very fast:

http://blog.fatalmind.com/2010/07/30/analytic-top-n-queries/