If you want to tune queries, you have to look at query plans and you have to understand what they’re showing you. One thing people look for when tuning is “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 on statistics and query plans. 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 issues. 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.
Erin Stellato, Principal Consultant SQLskills
Erin Stellato is a Data Platform MVP and lives outside Cleveland, OH. She has almost 20 years of technology experience and has worked with SQL Server since 2003. Her areas of interest include performance tuning, Query Store, Extended Events, and helping accidental/involuntary DBAs understand how SQL Server works. Erin is an active member of the SQL Server community, has volunteered for PASS at the local and national level, and is a regular speaker at conferences including the PASS Summit, SQLIntersection, and SQLBits. Outside of time with family and friends, she enjoys running, spinning, movies, and all things chocolate.