date value 18/5/2010, 1 pm 40 18/5/2010, 2 pm 20 18/5/2010, 3 pm 60 18/5/2010, 4 pm 30 18/5/2010, 5 pm 60 18/5/20
In Oracle:
This gets the key of the max(high_val) in the table according to the range.
select high_val, my_key from (select high_val, my_key from mytable where something = 'avalue' order by high_val desc) where rownum <= 1