D J Horton Consulting Ltd

Personal reference to useful tips and tricks for SQL Server, SQL Server Reporting Services and Crystal Reports.

My alternative to scraps of paper lying about.

Others may find bits of it useful!

Wednesday, 5 May 2010

Nth largest value - SSRS

I recently had a query regarding replicating Crystal Reports nth largest functionality in Reporting Services (hope this helps, Andy!).

For example, In Crystal Reports, its simply a case of using Insert>>Summary

I believe the most efficient way to go about is to use a subquery in T-SQL and incorporate into a dataset.

Using the AdventureWorks db, the first query uses the ROW_NUMBER function to sequentially order rows, purely for this examples sake. (ROW_NUMBER is only available in SQL Server 2005 onwards)

SELECT SalesPersonID, SalesYTD, ROW_NUMBER() OVER(ORDER BY SalesYTD desc) as rownum
FROM AdventureWorks.Sales.SalesPerson

The second query, using a subquery, firstly selects the top 3 SalesYTD values and then selects the smallest of these 3, the third largest of all values.

(SELECT TOP 3 SalesPersonID, SalesYTD FROM AdventureWorks.Sales.SalesPerson ORDER BY SalesYTD desc) as Sales

By simply replacing the 3 in the subquery by n, the nth largest value can be obtained.

1 comment:

Andy said...

I don't have much experience writing and understanding what the SQL syntax is all about. (I'm used to Crystal Reports after all) This solution forced me to educate myself a bit.

I did manage to get the solution implemented, and solved my immediate problem of returning the nth highest value, and increased my understanding of SQL from about a 1 to a 3.