FIX: SELECT ... UNION Produces Unexpected Output

WINDOWS   | MS-DOS    | MACINTOSH

The information in this article applies to:

• Microsoft FoxPro for Windows, versions 2.5x, 2.6
• Microsoft FoxPro for MS-DOS, versions 2.0, 2.5x, 2.6
• Microsoft FoxPro for Macintosh, version 2.5b

SYMPTOMS

The UNION clause of the SELECT statement can cause unexpected output under certain circumstances.

STATUS

Microsoft has confirmed this to be a problem in the products listed at the beginning of this article. This problem was corrected in FoxPro version 2.6a for MS-DOS and FoxPro version 2.6a for Windows.

MORE INFORMATION

Steps to Reproduce Problem

Executing the following code will demonstrate this problem:

  CREATE TABLE test1 (one c(1), two c(1), three c(1))
  INSERT INTO test1 VALUES ('a','b','c')

  CREATE TABLE test2 (one c(1), two c(1), three c(1))
  INSERT INTO test2 VALUES ('a','b','c')

  * Notice the output produced by this SELECT statement, which includes
  * the clause "UNION ALL".

  SELECT one,two,three FROM test1 UNION ALL ;
  SELECT one,one,three FROM test2 TO SCREEN

     ONE TWO THREE
     a   b   c
     a   a   c

  * Notice the output produced by this SELECT statement, which includes
  * the clause "UNION". It is different from the output produced by the
  * previous SELECT statement, which includes the clause "UNION ALL".

  SELECT one,two,three FROM test1 UNION ;
  SELECT one,one,three FROM test2 TO SCREEN

     TWO_A TWO_B THREE
     a     a     c
     b     b     c