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November 15-18

Seattle & online

2021 Summit video library

Demystifying Statistics in SQL Server

Erin Stellato

Troubleshooting performance issues and tuning queries can be easier with some level of understanding about statistics. Something you may hear people talk about as part of query tuning are “bad cardinality estimates”. If you’ve wondered what that means, and you want to understand how the optimizer uses statistics when creating a query plan, then join me for this session. We’ll set the stage with a review of what statistics are, then see how the optimizer uses them and where to find that “cardinality estimate” information in a plan. We’ll also cover the various ways statistics can be updated, explore what happens to plans when those updates occur, and ultimately you will see why understanding how it all works is critical when you’re troubleshooting performance problems. Expect lots of demos so you can truly understand what statistics are, how they’re used, and why their management is so essential for good performance.