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

• Microsoft Access versions 7.0, 97

SYMPTOMS

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

Code written in Access Basic that uses "-1" or "0" (with the quotation marks) 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

   If rs![yesnofield] = "0" Then

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" (with the quotation marks).

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 described below.

If you are using the following expression in Access Basic

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

   IF rs![yesnofield] = -1 Then

   -or-

   IF rs![yesnofield] = True Then

   IF rs![yesnofield] = "0" Then

   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