In one of the recent projects, I found out that despite putting good indexes and optimizing the query, I could not achieve an optimized performance and I still received an unoptimized response from the SQL Server. On examination, I figured out that the culprit was statistics. The database that I was trying to optimize had auto update of the statistics was disabled. Let us learn about how to Enable Automatic Statistic Update on Database.
Earlier I have written two different articles on the subject Remove Bookmark Lookup. This article is as part 3 of the original article. Please read the first two articles here before continuing reading this article.
You can download the poster from Itzik Ben-Gan’s T-SQL Querying page over here.
Earlier this year, I had written article on SQL SERVER – Logical Query Processing Phases – Order of Statement Execution and I had asked one question to readers. I got very good response for this question. Today, I am going to discuss about one of the errata I have made there. I had displayed the Logical Query Processing order, where I had incorrectly listed the last two operations. I have listed the operations as ORDER BY first and TOP afterwards. The fact is that TOP is always executed first and ORDER BY after that.