INF: How to Write a Variance Query in SQL Server

ID: Q175955

The information in this article applies to:

• Microsoft SQL Server versions 6.0 and 6.5

When you need to make a comparison between a value and the average for that value in the same category, you can execute a variance query. For example, you may want to use a variance query when you want to compare the salary of an employee against the salary of other employees who hold the same title, or when you want a comparison between the price of a book and the price of all the other books of the same category.

To continue the book example, you can execute the query below in the pubs database. Note that this is a correlated subquery, so it will take a while to run against a very large table.

   select
      title,
      price,
      variance = price - (select avg(price)
                                    from titles t2
                                    where t2.type = t1.type)
   from titles t1

Keywords          : kbusage SSrvGen 
Version           : WINNT:6.0 6.5
Platform          : winnt
Issue type        : kbhowto

Last Reviewed: January 9, 1998