PRB: Query Bases Result Set Field Size On Non-Included Values

ID: Q169791

The information in this article applies to:

Microsoft FoxPro for MS-DOS, versions 2.0, 2.5, 2.5a, 2.5b, 2.6, 2.6a
Microsoft FoxPro for Windows, versions 2.5, 2.5a, 2.5b, 2.6, 2.6a
Microsoft FoxPro for Macintosh, versions 2.5b, 2.5c, 2.6a
Microsoft Visual FoxPro for Macintosh, version 3.0b
Microsoft Visual FoxPro for Windows, versions 3.0, 3.0b, 5.0, 5.0a

SYMPTOMS

A query may result with truncated values in an expression columns.

CAUSE

The expression column is basing its width on the first record value of the source table.

RESOLUTION

Change the expression to use an IIF() function that returns a value of necessary width. This forces FoxPro to create a column wide enough to hold the results of the expression column. NOTE: The example code uses the table created at the bottom of this article in the MORE INFORMATION section. Here's an example:


   SELECT *, IIF(ISNULL(fld2),SPACE(15),TTOC(fld2,1)) AS test ;
   FROM temp WHERE fld2 is NOT NULL

-or-

Change the source table's order so that the first record's value in the source table is wide enough to hold the expression columns output. An index order cannot be used here, since FoxPro opens the source table in another workarea. Using an additional query can do this. Here's an example:


   SELECT * FROM temp ORDER BY fld2 DESCEND INTO CURSOR temp2
   SELECT *, TTOC(fld2,1) AS test FROM temp2

STATUS

Microsoft is researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

MORE INFORMATION

Steps to Reproduce Behavior

Execute the following five lines to create and populate a table:


      CREATE TABLE temp (fld1 C(3), fld2 T NULL, fld3 C(3))
      INSERT INTO temp (fld1, fld2, fld3) VALUES ('aaa',NULL,'aaa')
      INSERT INTO temp (fld1, fld2, fld3) VALUES ('bbb',datetime(),'bbb')
      INSERT INTO temp (fld1, fld2, fld3) VALUES ('ccc',NULL,'ccc')
      INSERT INTO temp (fld1, fld2, fld3) VALUES ('ddd',datetime(),'ddd')

Execute the following lines from the Command window:


      SELECT *, TTOC(fld2,1) AS test FROM temp
      SELECT *, TTOC(fld2,1) AS test FROM temp WHERE fld2 IS NOT NULL

Note that the test column comes up improperly sized for both queries. The test column is based solely on the width of the source table's first record, a 1 byte NULL character. Thus, the column shows only a 1 from the result of the TTOC() function.

This occurs even when records that contain NULL are not included in the result set, per the second query.

Additional query words:

Keywords : kbMAC kbVFp FoxDos FoxWin FxprgSql
Version : MACINTOSH:2.5b,2.5c,2.6a,3.0b; MS-DOS:2.0,2.5,2.5a,2.5b,2.6,2.6a; WINDOWS:2.5,2.5a,2.5b,2.6,2.6a,3.0,3.0b,5.0,5.0a
Platform : MACINTOSH MS-DOS WINDOWS
Issue type : kbprb