The goal of the DBA Virtual Group is to provide a PASS community for the DBA. It provides a forum for open discussion and education on issues that face SQL Server database administrators.

Think like the Cardinality Estimator – sponsored by Hewlett Packard Enterprise

Wed, Apr 26 2017 16:00 UTC

Think like the Cardinality Estimator

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 type of physical operations during a 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 happen 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 a value that is outside of histogram range? In this session, I will show you how 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.


Taiob Ali

Taiob Ali, an accomplished technical leader with proven record of success. He has spent the last 13 years working with SQL Server and MongoDB platform both on premise and cloud. His experience includes three major business sectors: financial industry, e-commerce and healthcare. Taiob has hands on experience in managing large database projects including large data migration, complex process design, testing and deployment, performance tuning, long term capacity planning. Taiob is currently working at “GMO LLC” as lead DBA. Focusing on automation, improving and streamlining operational workflow, plan and prepare for cloud migration. He is a regular speaker at local and virtual PASS chapters, SQL Saturdays and Azure conferences.

Interested in Presenting to the DBA VG?

We can always use people to give a talk at one of our bi-monthly events. If you are interested in giving a presentation, please send your title, a brief abstract and a brief bio to Sharon Dooley, dbavolunteer@sqlpass.org.

Want to become a member of the DBA VG Leadership team?

Members of this team moderate meetings and interact with the speakers during the Q&A sessions. Contact Sharon Dooley, dbavolunteer@sqlpass.org if you'd like to become part of the team.

Have a speaker to recommend?

Send the email address of the proposed speaker together with any relevant information about the speaker to Sharon Dooley, dbavolunteer@sqlpass.org.

 

Meeting Recordings

The DBA Virtual Chapter presentations are recorded. On the Meeting Archive page, you will find  .WMV files that can be viewed on-line. Select the event you are interested in, click the Show More button if it is visible, and the recording and any associated files will be visible.

Regular Meeting Schedule

The DBA Virtual Chapter holds two regular webinars each month. The first one is on the second Wednesday at noon, Mountain time and the second one is on the fourth Wednesday at noon, Eastern time. These 1 - 1¼ hour presentations include slides, demos and a time for questions and answers. The meetings are recorded and archived.

 

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