Microsoft KB Archive/932393

= FIX: You may experience poor performance after you install SQL Server 2005 Service Pack 1 =

Article ID: 932393

Article Last Modified on 11/20/2007

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APPLIES TO


 * Microsoft SQL Server 2005 Standard Edition
 * Microsoft SQL Server 2005 Standard X64 Edition
 * Microsoft SQL Server 2005 Developer Edition
 * Microsoft SQL Server 2005 Enterprise Edition
 * Microsoft SQL Server 2005 Enterprise Edition for Itanium-based Systems
 * Microsoft SQL Server 2005 Enterprise X64 Edition
 * Microsoft SQL Server 2005 Standard Edition for Itanium-based Systems Community Technology Preview

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Bug #: SQL Hotfix 50000820



Notice
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.



SUMMARY
This article describes the following about this hotfix release:
 * The issues that are fixed by this hotfix package
 * The prerequisites for installing the hotfix package
 * Whether you must restart the computer after you install the hotfix package
 * Whether the hotfix package is replaced by any other hotfix package
 * Whether you must make any registry changes
 * The files that are contained in the hotfix package



SYMPTOMS
In Microsoft SQL Server 2005, you may experience poor performance after you install SQL Server 2005 Service Pack 1 (SP1). This issue occurs when you run a query that has a CASE function in the WHERE clause. For example, you run a query that resembles the following: SELECT * FROM ( SELECT CASE                  WHEN col1 IS NULL THEN  3                  WHEN col1=0 THEN 3                  WHEN col1=2 THEN 0                  ELSE 3                  END Col2 FROM T1 WHERE col3 =N'') T2 WHERE col4 in(0,1,2)



CAUSE
A code change in SQL Server 2005 SP1 causes an incorrect cardinality estimate for the CASE function. This behavior causes an inefficient execution plan.



Hotfix information
A supported hotfix is now available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next service pack that contains this hotfix.

To resolve this problem, submit a request to Microsoft Online Customer Services to obtain the hotfix. To submit an online request to obtain the hotfix, visit the following Microsoft Web site:

http://go.microsoft.com/?linkid=6294451

Note If additional issues occur or any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. To create a separate service request, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support

Prerequisites
To apply this hotfix, you must have SQL Server 2005 Service Pack 1 installed. For more information about how to obtain SQL Server 2005 Service Pack 1, click the following article number to view the article in the Microsoft Knowledge Base:

913089 How to obtain the latest service pack for SQL Server 2005

Restart information
You do not have to restart the computer after you apply this hotfix.

Hotfix replacement information
This hotfix does not replace any other hotfixes.

File information
The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time item in Control Panel.

SQL Server 2005 hotfix, Itanium architecture versions


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 software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:

824684 Description of the standard terminology that is used to describe Microsoft software updates

Keywords: kbfix kbqfe kbpubtypekc kbhotfixserver kbsql2005engine kbsql2005tsql KB932393

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