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

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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 intasselect * 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.ColAgo

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.

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.
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.
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

Article ID: 822033 - Last Review: 02/27/2014 18:44:07 - Revision: 8.2

  • 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
  • kbnosurvey kbarchive kbqfe kbquery kbstoredproc kbsqlserv2000presp4fix kbfix kbbug KB822033