22-25 April 2026 
SQLBits 2017
Exploring Statistics: Where estimated rowcount comes from
A look inside SQL Server distribution statistics
Where do the estimated rowcount values come from? Look
inside SQL Server’s distribution statistics to see how they are used to come up
with the estimates. We’ll also discuss changes in the cardinality estimator in
recent versions and look at some new metadata that gives us more statistics
information.
Goals:
- Explore the output of DBCC SHOW_STATISTICS
- Describe when the density information is useful
- Look at some problem scenarios for which the statistics can’t give good estimates
- Understand why cardinality estimation involves more than just the statistics
Speakers
Kalen Delaney's previous sessions
Behind the Query Store…
Look inside Query Store to see what it does and how it works
Exploring Statistics: Where estimated rowcount comes from
A look inside SQL Server distribution statistics
What Happened? Exploring the Plan Cache
In this session, we'll explore SQL Server's plan cache, including techniques for discovering what plans are in cache, how often they've been run, and whether they contain any sub-optimal operators. Knowing what's happened is the first step in tuning.
Seeking SQL Server Secrets
In this session, I’ll tell you about some of my favorite undocumented features, and also tell you some of my tricks for discovering more undocumented secrets.