Think Like the Cardinality Estimator

The November meeting for the Ohio North Database Training user group will be on Tuesday, November 2, 2021. This will be a virtual event and our featured speaker will be Taiob Ali, Data Platform MVP.

5:30PM EDT: online meeting begins with a social hour. This is an unstructured hour where you can join us to catch up and meet other members of the group before the session starts.

6:30PM EDT: Updates and announcements, followed by Taiob's session.

**Slight time change! We are starting a half hour later than usual to accommodate schedules and election day voting.

Taiob's session will help you understand how the optimizer works with regard to cardinality estimation, and this is a valuable session for DBAs and developers! Please review the abstract below for more details.

We hope to see you there!

*Please note, we will be using Microsoft Teams for this month's meeting. You may want to join a few minutes early to ensure you do not have any issues.

Session Abstract:
SQL Server uses a phase during query optimization, called cardinality estimation (CE). This process makes estimates based on the statistics as to how many rows flow from one query plan iterator to the next. Knowing how CE generates these numbers will enable you to write better TSQL code and in turn, influence the type of physical operations during query execution. Based on that estimated rows, the query processor decides how to access an object, which physical join to use, how to sort the data. Do you know how the CE generates these numbers? If your query has only one predicate, the query optimizer will use the histogram to estimate how many rows will be qualified. What happens when you have multiple predicates, range predicates, variable values that are “NOT KNOWN” to the optimizer, or you have predicate values increasing in ascending order? Do you know what will happen if your predicate is using an amount that is outside of the histogram range?

In this session, I will show you how the cardinality estimator estimates in all of these scenarios. You will walk out of this session with a clear understanding of how the CE generates its numbers and ready to tackle those nasty, hard-to-solve query plans.

Speaker Bio:
Taiob Ali, Microsoft Data Platform MVP, is an accomplished technical leader with a proven record of success. During his last 16 years, he has worked with the Microsoft Data Platform and MongoDB, both on-premises and cloud. His experience includes all three major business sectors: finance, e-commerce, and healthcare.

Taiob is currently working at “GMO LLC” as Database Solutions Manager, focusing on cloud migration, automation, improving, and streamlining operational workflow. He is a regular speaker at local and virtual chapters, Data Saturdays, and Azure conferences. He is a board member of New England SQL Server User Group, founder of 'Database Professionals Virtual Meetup Group', and organizer of Boston SQL Saturday.

Blog: https://sqlworldwide.com/
Twitter: https://twitter.com/SqlWorldWide