Chapter 5

Query Processing and Execution


  • How SQL Server processes queries
  • Understanding query optimization
  • Reading query plans
  • Using options to affect query plans
  • Using plan hints to affect query plans


The code downloads for this chapter are found at on the Download Code tab. The code is in the Chapter 5 download and individually named according to the names throughout the chapter.

This section uses the AdventureWorks 2012 database, so now is a good time to download it from the SQL Server section on CodePlex if you haven’t already. The AdventureWorks 2012 samples can be found at


Query processing is one of the most critical activities that SQL Server performs in order to return data from your T-SQL queries. Understanding how SQL Server processes queries, including how they are optimized and executed, is essential to understanding what SQL Server is doing and why it chooses a particular way to do it.

In this chapter you will learn how SQL Server query processing works, including the details of query optimization and the various options that you can use to influence the optimization process; and how SQL Server schedules activities and executes them.


Query processing is performed by the Relational Engine in SQL Server. It is the process of taking the T-SQL statements you write and converting them ...

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