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
