ACC: Yes/No Field Not Evaluating "-1" or "0" in Comparisons

ID: Q142229

The information in this article applies to:

SYMPTOMS

Moderate: Requires basic macro, coding, and interoperability skills.

Code written in Access Basic that uses -1 or 0 to compare a Yes/No field in a table or recordset does not work properly when you convert the Access Basic code to Visual Basic for Applications code. In Microsoft Access version 2.0, which uses Access Basic, the numeric comparisons are evaluated as strings. In Microsoft Access 7.0 and 97, which uses Visual Basic for Applications, the numeric comparisons are evaluated as Boolean values.


CAUSE

In Access Basic the condition 


   If rs![yesnofield] = "-1" Then

is evaluated as True, and the condition: 

   If rs![yesnofield] = "0" Then

is evaluated as False.

In Visual Basic for Applications, these conditions are no longer evaluated in this manner.


RESOLUTION

In an open Access Basic or Visual Basic for Application Module window, use the Find command on the Edit menu (or press CTRL+F) to check for instances of the strings -1 or 0.

Change all instances in Visual Basic for Applications where "-1" or "0" is used to compare a Yes/No field in a table or recordset as follows.

If you are using the following expression in Access Basic 


   IF rs![yesnofield] = "-1" Then

in Visual Basic for Applications, change the code so that there are no quotation marks around the number "-1" or use the word "True" as in the following example: 

   IF rs![yesnofield] = -1 Then

   -or-

   IF rs![yesnofield] = True Then

If you are using the following expression in Access Basic 

   IF rs![yesnofield] = "0" Then

in Visual Basic for Applications, change the code so that there are no quotation marks around the number "0" or use the word "False" as in the following example: 

   IF rs![yesnofield] = 0 Then

   -or-

   IF rs![yesnofield] = False Then


STATUS

This behavior is by design.


MORE INFORMATION

Steps to Reproduce Behavior


  1. Start Microsoft Access 2.0 and open the sample database NWIND.MDB.


  2. Open the Products form in Design view and set the form's OnCurrent property to the following event procedure: 
    
      Sub Form_Current()
      Dim rs As Recordset
         Set rs = Me.RecordsetClone
         rs.Bookmark = Me.Bookmark
         If rs![Discontinued] = "-1" Then
            MsgBox "This product is discontinued."
         End If
         Set rs = Nothing
      End Sub


  3. Open the Products form in Form view and, using the record selectors, move through the records. Note that a message box appears for all discontinued products.


  4. Start Microsoft Access 7.0 or 97, and repeat steps 1-3. In step 2, change the first line of code that reads 
    
      Sub Form_Current()

   to read as follows:

      Private Sub Form_Current()


  5. Open the Products form in Form view and, using the record selectors, move through the records. Note that the message box for the discontinued products does not appear.



REFERENCES

For more information about the Boolean data type, search the Help Index for "Boolean data type," or ask the Microsoft Access 97 Office Assistant 


Keywords          : kbusage 
Version           : 7.0 97
Platform          : WINDOWS 
Issue type        : kbprb

Last Reviewed: April 29, 1999