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Is Distinct Aggregation Still Considered Harmful?
Back in 2008, Marc Friedman of the SQL Server Query Processor Team wrote a blog entry entitled “Distinct Aggregation Considered Harmful”, in which he shows a way to work around the poor performance that often results simply from adding the keyword DISTINCT to an otherwise perfectly reasonable aggregate function in a query. This post is an ...
Paul White: Page Free Space
December 3, 2011
Why generalizations are dangerous
A couple of years ago, John Sansom wrote a blog post comparing the performance of two different ways to get the maximum value from a column: MAX() and TOP (1). http://www.johnsansom.com/performance-comparison-of-select-top-1-verses-max/ In the conclusion, he states: When a clustered index is present on the table & ...
September 15, 2011
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