FIX: UNION query returns internal query processor error message 8623 (286255)

SYMPTOMS

A query statement may fail with error message 8623 if the following conditions are met:

The query uses the UNION clause.
One of the SELECT statements in the UNION query has a WHERE clause that refers to a subquery through an IN clause.
The SQL Server query optimizer chooses a loop join to resolve the query.

The complete text of the error message is:

Server: Msg 8623, Level 16, State 1, Line 1 Internal Query Processor Error: The query processor could not produce a query plan. Contact your primary support provider for more information.

RESOLUTION

Service pack information

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

290211 How to obtain the latest service pack for SQL Server 2000

Hotfix information

A supported fix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Apply it only to computers that are experiencing this specific problem. This fix may receive additional testing. Therefore, if you are not severely affected by this problem, Microsoft recommends that you wait for the next SQL Server service pack that contains this hotfix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS

NOTE: In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The typical support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

The English version of this fix should have the following file attributes or later:

   Date         Time     Version    Size      File name      Platform
   -------------------------------------------------------------------

   01/13/2001   12:52a   8.00.240   7446589   Sqlservr.exe   Intel

NOTE: Due to file dependencies, the most recent hotfix or feature that contains the preceding files may also contain additional files.

WORKAROUND

To work around this behavior:

Rewrite the query statement and use a join instead of the IN clause subquery.

-or-

Use the OPTION optimizer hint to force a hash union. The example query in the "More Information" section would change to:

SELECT P.EMP_NO, N.ADJ_SCON
  FROM   BATCH_EMPEE P, EMPLOYEE E, NI_CONDITION N
  WHERE  E.EMP_NO = P.EMP_NO AND
         N.EMP_NO = E.EMP_NO AND
         P.JOB_ID = 25 AND
         N.PAYRUN_NO = 0

  UNION

  SELECT P.EMP_NO, ''
  FROM   BATCH_EMPEE P, EMPLOYEE E
  WHERE  E.EMP_NO = P.EMP_NO AND
         P.JOB_ID = 25 AND
         E.EMP_NO NOT IN
             (SELECT EMP_NO FROM NI_CONDITION WHERE PAYRUN_NO = 0)

  OPTION (HASH UNION)

MORE INFORMATION

The following query is an example for a statement that might lead to error message 8623:

SELECT P.EMP_NO, N.ADJ_SCON
  FROM   BATCH_EMPEE P, EMPLOYEE E, NI_CONDITION N
  WHERE  E.EMP_NO = P.EMP_NO AND
         N.EMP_NO = E.EMP_NO AND
         P.JOB_ID = 25 AND
         N.PAYRUN_NO = 0

  UNION

  SELECT P.EMP_NO, ''
  FROM   BATCH_EMPEE P, EMPLOYEE E
  WHERE  E.EMP_NO = P.EMP_NO AND
         P.JOB_ID = 25 AND
         E.EMP_NO NOT IN
             (SELECT EMP_NO FROM NI_CONDITION WHERE PAYRUN_NO = 0)