ACC: Null Value Does Not Pass Validation Rule

• Microsoft Access versions 2.0, 7.0, 97

SYMPTOMS

Novice: Requires knowledge of the user interface on single-user computers.

You cannot leave a field blank, or Null, in a table's Datasheet view if the field has a validation rule.

CAUSE

This behavior only occurs when adding a new record with two fields, one of which has a data type of AutoNumber (or Counter in version 2.0).

This behavior differs from that of Microsoft Access version 1.x. In Microsoft Access 1.x, a Null value is accepted for a field even if "Or Is Null" is not part of the validation rule.

RESOLUTION

Include "Or Is Null" as part of the validation rule for the field. For example, a validation rule for a text field could be:

   "A" Or "B" Or Is Null

STATUS

This behavior is by design.

MORE INFORMATION

Steps to Reproduce Behavior

1. Create the following new table and save it as Table1:

         Table: Table1
         ---------------------------------------------------
         Field Name: ID
            Data Type: AutoNumber (or Counter in version 2.0)
         Field Name: Code
            Data Type: Text
            Validation Rule: "A" Or "B" Or Is Null
   
   

2. View the table in Datasheet view.

3. Select the Code field. Type "A" (without the quotation marks) and press ENTER. Note that you can move to the next record.

4. In the next record, press TAB to move to the third record. Note that you cannot move to the next record because the Code field cannot initially be Null. This is because there is only one user input field defined in this table, and the record cannot be saved until it has received some input.

5. Select the Code field in the second record. Type "A" (without the quotation marks) and press ENTER. Delete the "A" from the field, and press TAB. Note that you can move to the next record now because the record was initially saved with data.

REFERENCES

For more information about the ValidationRule property, search for "ValidationRule property," and then "Create a validation rule for a control" using the Microsoft Access 97 Help Index.