I am going to design a Data Warehouse and I heard about materialized views. Actually I want to create a view and it should update automatically when base tables are changed. Can anyone explain with a query example?
They're called indexed views in SQL Server - read these white papers for more background:
Basically, all you need to do is:
and you're done!
The tricky part is: the view has to satisfy quite a number of constraints and limitations - those are outlined in the white paper. If you do this, that's all there is. The view is being updated automatically, no maintenance needed.
Additional resources: