Ranking Functions

With SQL Server, it’s possible to rank rows of data in your T-SQL code. Ranking functions give you the ability to rank each row of data to provide a method of organizing the output in an ascending sequence. You can give each row a unique number or each group of similar rows the same number. You may be wondering what is wrong with other methods of ranking data, which might include IDENTITY columns. These types of columns do provide unique numbers, but gaps can form. You are also tied into each row having its own number, when you may want to group rows together.

So then, why not use GROUP BY? Well, yes, you can use GROUP BY, but what if the grouping was over more than one column? In this case, processing the data further would require knowledge about those columns. Ranking functions make it possible to provide a value that allows data to be ranked in the order required, and then that value can be used for splitting the data into further groupings.