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
Enterprise AI Operating Rhythm – Top 5 practices for 2026
2025 exposed a growing gap between AI ambition and operational reality. As budgets tightened...
Stop Being Surprised by Your Azure Bill: Use Budgets
By John
When organizations migrate workloads to Azure, the focus is usually on architecture, performance, and...
Resetting on the AI hype train
By Brian Kelley
There's a great article from MIT Technology Review about resetting on the hype of...
Forums
The Max PK Length
Comments posted to this topic are about the item The Max PK Length
My experience using the GitHub Copilot in SSMS 22
Comments posted to this topic are about the item My experience using the GitHub...
The Microsoft SQL Year in Review
Comments posted to this topic are about the item The Microsoft SQL Year in...
Question of the Day
The Max PK Length
If I create a multiple column Primary Key constraint, what is the most number of bytes I can include in the constraint?
See possible answers