Inside Microsoft® SQL Server™ 2005: T-SQL Querying

Logical Query Processing Phases

This section introduces the phases involved in the logical processing of a query. I will first briefly describe each step. Then, in the following sections, I’ll describe the steps in much more detail and apply them to a sample query. You can use this section as a quick reference whenever you need to recall the order and general meaning of the different phases.

Example 1-1 contains a general form of a query, along with step numbers assigned according to the order in which the different clauses are logically processed.

Example 1-1. Logical query processing step numbers

(8)  SELECT (9) DISTINCT (11) <TOP_specification> <select_list>
(1)  FROM <left_table>
(3)    <join_type> JOIN <right_table>
(2)      ON <join_condition>
(4) WHERE ...