Hugo Kornelis

Information & Communications Technology

SQL Server Azure SQL Azure SQL Database Azure SQL DB SQL SQL Server DBA performance tuning Indexing

Zeewolde, Flevoland, Netherlands

Now Where Did THAT Estimate Come From?

The SQL Server Query Optimizer makes its plan choices based on estimated rowcounts. If those estimates are wrong, the optimizer will very likely produce a poor plan. And there's nothing you can do about it. Or is there?
In this session, you will learn exactly where these estimates come from. You will gain intimate knowledge of how statistics are built and maintained and how they are used to estimate row counts. But you will also learn how filters and joins influence those estimates.
Though the focus of this session is on understanding the cause of bad estimates, you will also learn ways to fix the problems and get better estimates - and hence, better performing queries.


Hugo Kornelis

I make SQL Server fast (.com)

Hugo Kornelis is an established SQL Server communiity expert who spends a lot of time at various conferences. He is also a blogger, technical editor of a variety of books, and Pluralsight author. He was awarded SQL Server MVP and Data Platform MVP 12 times (2006 - 2016 / 2019 - now).

When not working for the community, he is busy at his day job: freelance database developer/consultant.

Hugo has over 20 years of SQL Server experience in various roles. He has a strong database design background, but also loves to write and tune complex queries.

Hugo's full speaker profile