Q165066: FIX: Subquery Causes SUM to Return Incorrect Results

Article: Q165066
Product(s): Microsoft FoxPro
Version(s): WINDOWS:5.0
Operating System(s): 
Keyword(s): kbvfp500aFIX kbvfp500bugkbbuglist kbfixlist
Last Modified: 04-FEB-2000

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The information in this article applies to:

- Microsoft Visual FoxPro for Windows, version 5.0 
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SYMPTOMS
========

Including a subquery with a SQL-SELECT statement containing a SUM command causes
the SUM command to report incorrect amounts.

STATUS
======

Microsoft has confirmed this to be a problem in the Microsoft products listed at
the beginning of this article. This problem was corrected in Visual FoxPro 5.0a
for Windows.

MORE INFORMATION
================

The following code creates a table, populates it with data, and performs a
SELECT-SQL statement containing a subquery.

Steps to Reproduce Behavior
---------------------------

Create a program containing the following lines of code and execute it:

     *** Begin program code

     CLOSE ALL
     CREATE CURSOR Master ( nId I, cName C(10))
     INSERT INTO Master VALUES ( 1, "One")
     INSERT INTO Master VALUES ( 2, "Two")
     INSERT INTO Master VALUES ( 3, "Three")
     INSERT INTO Master VALUES ( 4, "Four")

     CREATE CURSOR Results ( nId I, dDate D)
     INSERT INTO Results VALUES ( 1, DATE())
     INSERT INTO Results VALUES ( 1, DATE())
     INSERT INTO Results VALUES ( 1, DATE())
     INSERT INTO Results VALUES ( 1, DATE())
     INSERT INTO Results VALUES ( 2, DATE() + 3)
     INSERT INTO Results VALUES ( 2, DATE() + 3)
     INSERT INTO Results VALUES ( 2, DATE() + 3)

     CREATE CURSOR Detail ( nId I, nAmount Y)
     INSERT INTO Detail VALUES ( 1, 100.00)
     INSERT INTO Detail VALUES ( 3, 300.00)

     * This will show correct sums
     WAIT WINDOW "Correct:" timeout 3
     SELECT Master.cName, ;
        SUM( NVL( Detail.nAmount, 0)) AS nSum ;
        FROM Master LEFT OUTER JOIN Detail ON Detail.nId = Master.nId ;
        GROUP BY 1

     * However, if I add an additional subquery, sum results are wrong.
     WAIT WINDOW "w/ Subquery - Wrong under VFP 5.0:" timeout 3
     SELECT Master.cName, ;
        SUM( NVL( Detail.nAmount, 0)) AS nSum ;
        FROM Master LEFT OUTER JOIN Detail ON Detail.nId = Master.nId ;
        WHERE Master.nId IN ( SELECT DISTINCT nId FROM Results ) ;
        GROUP BY 1

     CLOSE ALL
     *** End of program code

Executing the first query in Visual FoxPro 5.0 gives the following results:

  Cname       Nsum
  -----       -----
  Four        0.0000
  One         100.000
  Three       300.000
  Two         0.00000

The second query in Visual FoxPro 5.0, which contains the subquery, gives the
following incorrect results based on the same data:

  Cname       Nsum
  -----       -----
  One         0
  Two         0

In Visual FoxPro 5.0a, the results of the first query remain the same. However,
the second query correctly returns to following values:

  Cname       Nsum
  -----       -----
  One         100.0000
  Two         0.0000

Additional query words: 5.0

======================================================================
Keywords          : kbvfp500aFIX kbvfp500bug kbbuglist kbfixlist
Technology        : kbVFPsearch kbAudDeveloper kbVFP500
Version           : WINDOWS:5.0
Issue type        : kbbug
Solution Type     : kbfix

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