I am speaking today at SSSLUG on Excution Plans

Today the sessions include an introduction to Denali and the second part of Execution Plans Explained. Today's session focuses on specific items in the execution plan:  Seeks, Scans and Physical Join operators.

What SSWUG.ORG Says About My Article?

Hope you've read my blog about (Mis) Understanding Scans and Seeks.  This is about my article recently published at sql server performance. As the title was "understanding scans and seeks" many would have thought that it is all about the basics of scans and seeks and simply skipped it. However, SQL Server Worldwide User Group (SSWUG.ORG) recognized something about the value of thearticle and added it in its collection with a simple one line comment:
http://www.sswug.org/articles/extarticle.aspx?id=46032

Thinking about reading it again or at least now?

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The Tipping Point.

Many DBAs have faced with execution plans where it was an index seek for many days suddenly it became an index scan. (or vice versa). So when and how SQL Server decides what to use? (I am not talking about re-writing the query in different way so that the execution plan can get changed. it is the same query suddenly gets a new execution plan.)

SQL Server keeps statistics to determine the best method. When the data requested is beyond a particular percentage, the decision to scan is taken.

Interesting? Kimberly L. Tripp a great speaker, trainer and writer in SQL Server gives some more information:

http://www.sqlskills.com/BLOGS/KIMBERLY/category/The-Tipping-Point.aspx

(Mis) Understanding Scans and Seeks

Have you ever expected an index seek or clustered index seek for a query, where SQL Server turned its back and decided to use scan?
Do you believe in this statement: "Scan reads through the object (table/index) from top to bottom looking for the records that it needs while seek goes directly to the part of the object that it needs and reads to where the data that it needs ends. This is obviously a must more efficient operation than a scan, as database server already knows where the data is that it is looking for"

If your answer is true for any of the questions, you need to read my article.
http://www.sql-server-performance.com/articles/dba/understanding_scans_seeks_p1.aspx

As the above site does not allow reader feedback, I am opening this area for your comments

Index /Clustered Index SCAN When Top 1 Is Used

One of my recent articles is published at SQL Server Worldwide User Group.

Even a simple statement which SELECTs the last (or first) row of a table may cause clustered index scan or index scan. But there are ways to make it a seek.

Interested?? Have a look at http://www.sswug.org/see/37061

The site may request you to be a member to read the article. But eventhough you may have to give your credit card details, You can have a free trial membership.

If you dont like the site, you can cancel the membership without paying any money.