SELECT ProductSales FROM [Sales by Category] WHERE ProductName = ''''Chai''''
Queries performing aggregations can be harder to optimize than other queries. Using can a view can not only hide the complexity but can also ensure anyone who needs the aggregation will be using an optimized query.
With SQL Server 2000 Enterprise Edition you can also receive a huge performance boost by aggregating data with a view and applying an index. The first index to apply to a view is a clustered index. A clustered index will materialize the view. In other words, the index will persist the data in a view to disk. An indexed view can dramatically decrease the amount of time needed to aggregate data as the index already has the sorted, grouped, and calculated results. The drawbacks to watch for include increased disk space, and more overhead on INSERT, UPDATE, and DELETE statements on the view’s base tables, because the database might need to update the index.
Summary
Views are a useful tool to have in your database tool arsenal. More portable than functions, more flexible than stored procedures, view can give your database more secure, more performant, and easier to use.
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