SQL Server 2005 ranking functions - RANK(), DENSE_RANK(), NTILE()

http://msdn.microsoft.com/en-us/library/ms189798.aspx
Ranking functions return a ranking value for each row in a partition. Depending on the function that is used, some rows might receive the same value as other rows. Ranking functions are nondeterministic.


Good explanation of ranking function

Good example of ranking function