Sample Example of RANKING Functions – ROW_NUMBER, RANK, DENSE_RANK, NTILE

I have not written about this subject for long time, as I strongly believe that Book On Line explains this concept very well. SQL Server 2005 has total of 4 ranking function. Ranking functions return a ranking value for each row in a partition. All the ranking functions are non-deterministic.

ROW_NUMBER () OVER ([<partition_by_clause>] <order_by_clause>)
Returns the sequential number of a row within a partition of a result set, starting at 1 for the first row in each partition.

RANK () OVER ([<partition_by_clause>] <order_by_clause>)
Returns the rank of each row within the partition of a result set.

DENSE_RANK () OVER ([<partition_by_clause>] <order_by_clause>)
Returns the rank of rows within the partition of a result set, without any gaps in the ranking.

NTILE (integer_expression) OVER ([<partition_by_clause>] <order_by_clause>)
Distributes the rows in an ordered partition into a specified number of groups.

More Details:

http://blog.sqlauthority.com/2007/10/09/sql-server-2005-sample-example-of-ranking-functions-row_number-rank-dense_rank-ntile/