SQL Server 6.5 Performance Optimization and Tuning Handbook
An explanation of fundamental performance tuning concepts for SQL Server targeted to intermediate level database developers and administrators.
TABLE OF CONTENTS SQL Server 6.5 Performance Optimization and Tuning Handbook
Section 4.2.1: The First Step: Query Analysis
4.2.1 The First Step: Query Analysis
The first step that the query optimizer performs during the query optimization phase is query analysis. In this step the query optimizer examines the query for search arguments (SARGs), the use of the OR operator and join conditions.
4.2.1.1 Search Arguments
A search argument is that part of a query that restricts the result set. If indexes have been chosen carefully, an index can be used to support the search argument. Examples of search arguments are:
account_no = 7665332 balance > 30 lname = 'Burrows'
The AND operator can be used to connect conditions so another example of a valid search argument would be:
balance > 30 AND lname = 'Burrows'
Examples of common operators that are valid in a search argument are =, >, <, <= and >=. Other operators such as BETWEEN and LIKE are also valid because the query optimizer can represent them with the common operators listed above. For example, a BETWEEN can always be represented as >= AND <=. For example:
balance BETWEEN 1000 AND 10000
becomes:
balance >= 1000 AND balance <= 10000
A LIKE can always be represented as >= AND < For example:
lname LIKE 'Burr%'
becomes:
lname >= 'Burr' AND lname < 'Burs'
| Hint | The expression balance BETWEEN 1000 AND 10000 is not equivalent to balance BETWEEN 10000 AND 1000. |
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