FIX: A Parameterized UNION Query Inside a Stored Procedure Returns Incorrect Results

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Article ID: 822033 - View products that this article applies to.
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SYMPTOMS

When you run a stored procedure on a multi-processor computer, the stored procedure may return an incorrect number of rows, or incorrect results, if the following conditions are true:
  • The stored procedure has a query that runs in parallel.
  • The query creates a derived table and the table is the result of a UNION or a UNION ALL operation.
  • At least one branch of the UNION query uses a parameter value passed to the procedure as a constant expression in its SELECT list.
  • The derived table generated by the UNION query is joined with another table using a column that returns one of the constant parameter values passed to the procedure.
  • The query uses a hash join strategy that relies on partitioning by the join column.

This query is an example of the syntax that may cause the behavior to occur:
create procedure example_proc @P1 int
as
select * from 
				    ( select @P1 as x, ColB as y from T1
          union all
          select ColA as x, ColB as y from T2
        ) as DerivedT
 Join T3 
    on DerivedT.x = T3.ColA
go

RESOLUTION

Service pack information

To resolve this problem, obtain the latest service pack for Microsoft SQL Server 2000. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:
290211 How to obtain the latest SQL Server 2000 service pack

Hotfix 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 tool in Control Panel.
   Date         Time   Version         Size             File name
   ---------------------------------------------------------------------------
   31-May-2003  18:45  2000.80.818.0      78,400 bytes  Console.exe      
   25-Jun-2003  01:01  2000.80.818.0      33,340 bytes  Dbmslpcn.dll     
   25-Apr-2003  02:12                    786,432 bytes  Distmdl.ldf
   25-Apr-2003  02:12                  2,359,296 bytes  Distmdl.mdf
   30-Jan-2003  01:55                        180 bytes  Drop_repl_hotfix.sql
   23-Jun-2003  22:40  2000.80.837.0   1,557,052 bytes  Dtsui.dll        
   23-Jun-2003  22:40  2000.80.837.0     639,552 bytes  Dtswiz.dll       
   24-Apr-2003  02:51                    747,927 bytes  Instdist.sql
   03-May-2003  01:56                      1,581 bytes  Inst_repl_hotfix.sql
   08-Feb-2003  06:40  2000.80.765.0      90,692 bytes  Msgprox.dll      
   01-Apr-2003  02:07                      1,873 bytes  Odsole.sql
   05-Apr-2003  01:46  2000.80.800.0      62,024 bytes  Odsole70.dll     
   07-May-2003  20:41  2000.80.819.0      25,144 bytes  Opends60.dll    
   02-Apr-2003  21:48  2000.80.796.0      57,904 bytes  Osql.exe         
   02-Apr-2003  23:15  2000.80.797.0     279,104 bytes  Pfutil80.dll     
   22-May-2003  22:57                     19,195 bytes  Qfe469571.sql
   11-Jul-2003  17:04                  1,084,147 bytes  Replmerg.sql 
   04-Apr-2003  21:53  2000.80.798.0     221,768 bytes  Replprov.dll     
   08-Feb-2003  06:40  2000.80.765.0     307,784 bytes  Replrec.dll      
   11-Jul-2003  16:56                  1,085,925 bytes  Replsys.sql
   01-Jun-2003  01:01  2000.80.818.0     492,096 bytes  Semobj.dll       
   31-May-2003  18:27  2000.80.818.0     172,032 bytes  Semobj.rll
   29-May-2003  00:29                    115,944 bytes  Sp3_serv_uni.sql
   01-Jun-2003  01:01  2000.80.818.0   4,215,360 bytes  Sqldmo.dll       
   07-Apr-2003  17:44                     25,172 bytes  Sqldumper.exe    
   19-Mar-2003  18:20  2000.80.789.0      28,672 bytes  Sqlevn70.rll
   02-Jul-2003  00:18  2000.80.834.0     180,736 bytes  Sqlmap70.dll     
   08-Feb-2003  06:40  2000.80.765.0      57,920 bytes  Sqlrepss.dll    
   10-Jul-2003  22:00  2000.80.840.0   7,553,105 bytes  Sqlservr.exe    
   08-Feb-2003  06:40  2000.80.765.0      45,644 bytes  Sqlvdi.dll      
   25-Jun-2003  01:01  2000.80.818.0      33,340 bytes  Ssmslpcn.dll     
   01-Jun-2003  01:01  2000.80.818.0      82,492 bytes  Ssnetlib.dll     
   01-Jun-2003  01:01  2000.80.818.0      25,148 bytes  Ssnmpn70.dll     
   01-Jun-2003  01:01  2000.80.818.0     158,240 bytes  Svrnetcn.dll     
   31-May-2003  18:59  2000.80.818.0      76,416 bytes  Svrnetcn.exe     
   30-Apr-2003  23:52  2000.80.816.0      45,132 bytes  Ums.dll          
   02-Jul-2003  00:19  2000.80.834.0      98,816 bytes  Xpweb70.dll      
				
Note Because of file dependencies, the most recent hotfix or feature that contains the files may also contain additional files.

WORKAROUND

To work around the problem, use any of the following methods:
  • Disable query parallelism for the query by adding the OPTION (MAXDOP 1) query hint. This will produce the same result as the bug fix. The bug fix detects whether the MAXDOP option is set to 1, and automatically disables parallelism for this type of query.
  • Store the parameters of the stored procedure in local variables, and pass the local variables to the query as parameters.
  • Force a different join strategy, such as a loop join or a merge join.

STATUS

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.This problem was first corrected in Microsoft SQL Server 2000 Service Pack 4.

MORE INFORMATION

For additional information, 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

Properties

Article ID: 822033 - Last Review: February 27, 2014 - Revision: 8.2
APPLIES TO
  • Microsoft SQL Server 2000 Developer Edition
  • Microsoft SQL Server 2000 Standard Edition
  • Microsoft SQL Server 2000 Enterprise Edition
  • Microsoft SQL Server 2000 Personal Edition
  • Microsoft SQL Server 2000, Workgroup Edition
  • Microsoft SQL Server 2000 Desktop Engine (Windows)
  • Microsoft SQL Server 2000 Enterprise Edition 64-bit
Keywords: 
kbnosurvey kbarchive kbqfe kbquery kbstoredproc kbsqlserv2000presp4fix kbfix kbbug KB822033

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