Microsoft KB Archive/942659

= FIX: The query performance is slower when you run the query in SQL Server 2005 than when you run the query in SQL Server 2000 =

Article ID: 942659

Article Last Modified on 10/19/2007

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APPLIES TO


 * Microsoft SQL Server 2005 Enterprise Edition
 * Microsoft SQL Server 2005 Developer Edition
 * Microsoft SQL Server 2005 Standard Edition
 * Microsoft SQL Server 2005 Workgroup Edition

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Bug #: 50001716 (SQL Hotfix)



Microsoft distributes Microsoft SQL Server 2005 fixes as one downloadable file. Because the fixes are cumulative, each new release contains all the hotfixes and all the security fixes that were included with the previous SQL Server 2005 fix release.



SYMPTOMS
Consider the following scenario. You have a parameterized query. In the WHERE clause of the query, you specify the following search conditions:
 * You use a comparison operator to compare the value of a column to the value of a parameter.
 * You use the LIKE operator to match the value of the same column to the value of a different parameter.

For example, the query contains the following statements. DECLARE @para1 VARCHAR(50) DECLARE @para2 VARCHAR(50)

SET @para1 = 'Ad%' SET @para2 = 'A'

SELECT * FROM Person.Contact WHERE (LastName LIKE @para1) AND (LastName > @para2) In this scenario, the query performance is slower when you run the query in Microsoft SQL Server 2005 than when you run the query in Microsoft SQL Server 2000. For example, when you run the query in SQL Server 2000, the query takes 1.2 seconds to finish running. When you run the query in SQL Server 2005, the query takes 9 seconds to finish running.



CAUSE
This problem occurs because the execution plan that SQL Server 2005 uses for the query is less optimal than the execution plan that SQL Server 2000 uses for the query.

In SQL Server 2005, the execution plan uses the comparison operator to seek tables. In SQL Server 2000, the execution plan uses the LIKE operator to seek tables. The comparison operator returns more rows than the LIKE operator returns. Therefore, the query performance is slower.



RESOLUTION
The fix for this issue was first released in Cumulative Update 4. For more information about how to obtain this cumulative update package for SQL Server 2005 Service Pack 2, click the following article number to view the article in the Microsoft Knowledge Base:

941450 Cumulative update package 4 for SQL Server 2005 Service Pack 2

Note Because the builds are cumulative, each new fix release contains all the hotfixes and all the security fixes that were included with the previous SQL Server 2005 fix release. Microsoft recommends that you consider applying the most recent fix release that contains this hotfix. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

937137 The SQL Server 2005 builds that were released after SQL Server 2005 Service Pack 2 was released

Microsoft SQL Server 2005 hotfixes are created for specific SQL Server service packs. You must apply a SQL Server 2005 Service Pack 2 hotfix to an installation of SQL Server 2005 Service Pack 2. By default, any hotfix that is provided in a SQL Server service pack is included in the next SQL Server service pack.

After you install Cumulative Update 4, you must enable trace flag 4119. After you enable trace flag 4119, the execution plan uses the LIKE operator to seek tables in SQL Server 2005.

For more information about trace flags in SQL Server 2005, visit the following Microsoft Developer Network (MSDN) Web site:

http://msdn2.microsoft.com/en-us/library/ms188396.aspx



STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the &quot;Applies to&quot; section.



MORE INFORMATION
For more information about what files are changed, and for information about any prerequisites to apply the cumulative update package that contains the hotfix that is described in this Microsoft Knowledge Base article, click the following article number to view the article in the Microsoft Knowledge Base:

941450 Cumulative update package 4 for SQL Server 2005 Service Pack 2

