SSRS Best Practice - Data Calculations/Aggregatopm in SQL SP or in SSRS Expressions (VS/Report Builder)

Question

Should I try to do all (or as many as possible) necessary calculations for an SSRS report in SQL code (stored procedures) like summing, percentages etc. or should I do the calculations using Expressions in Report Builder/VS?

Is there an advantage to doing one over the other?

In other words, should I try to keep the data in my Datasets very granular, detailed, low level and then just use Report Builder 3.0/VS to do all the necessary calculations/aggregations?

Answer 1

There is no one-size-fits-all best approach. In a lot of cases, SQL will be faster at performing aggregations than SSRS. SSRS will be faster at performing the kind of operations that would cause a table scan instead of an index seek when it's done in SQL.

Experience, common sense, and testing are the best guides.

Answer 2

Almost always you want to do your filtering and calcs on the server side. If you do it through a stored procedure SQL Server can optimize the query and create a well prepared, reusable, query plan. You can examine the resulting query plan and optimize it. None of this is possible if you create and run the code on the client side. How will it use indexes on the client? If your report uses a lot of data your report will take a much longer time to run and your users will blame you. The editor in BIDS is much poorer then the one in SSMS. Procs can be backed up and managed through SVN of TFS. Unless you know for sure that it runs faster on the client (and this is very rare) learn how to create stored procedures.