Finding the latest / max records
I've just came up with aniother problem of getting a set of results. Finding the latest records, Example:

ID	Mobileno	created
1	+90990	01-FEB-06
2	+90990	02-FEB-06
3	+90991	02-FEB-06
4	+90991	01-FEB-06

The results must be like this , only 1 mobileno with the latest creation date

ID	Mobileno	created
2	+90990	02-FEB-06
3	+90991	02-FEB-06

The answer:
select t.*
from (select a.*,dense_rank() over (partition by mobileno order by created desc) dr from my_table a) t
where dr=1;