Cardinality Estimation for a Predicate on a COUNT Expression
Paul White takes you on an optimizer journey, exploring how SQL Server comes up with cardinality estimates for COUNT queries.
2017-05-17
3,222 reads
Cardinality Estimates
Bad Cardinality Estimates from SSMS Plans – Redux
Aaron Bertrand shares some insight about early changes to Plan Explorer that help to provide you with the most accurate information we can.
2016-04-04
2,780 reads
Fixing Gatekeeper Row Cardinality Estimate Issues
The Query Optimiser needs a good estimate of the number of rows likely to be returned by each physical operator in order to select the best query plan from the most likely alternatives. Sometimes these estimates can go so wildly wrong as to result in a very slow query. Joe Sack shows how it can happen with SQL Queries on a data warehouse with a star schema.
2012-12-10
1,163 reads
Blogs
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Introducing azsql-migration-test: Test and Validate Azure SQL Database Migrations
Introducing azsql-migration-test, a small open-source CLI that validates your Azure SQL Database migrations against...
Rambling about Data on Wheels – origins, branding, expansion
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I have been asked many times about how the name “Data on Wheels” came...
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DBCC CHECKDB Limits III
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CROSS APPLY Fundamentals: Part 1
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Question of the Day
DBCC CHECKDB Limits III
On SQL Server 2025, does DBCC CHECKDB support Memory-Optimized tables?
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