Testing Validation Rule Changes
You learned in Chapter 27 how to define both field and table validation rules. You can also change these rules even after you have data in your table. Access 2007 warns you if some of the data in your table doesn’t satisfy the new rule, but it doesn’t tell you which rows have problems.
Checking a New Field Validation Rule
The best way to find out if any rows will fail a new field validation rule is to write a query to test your data before you make the change. The trick is you must specify criteria that are the converse of your proposed rule change to find the rows that don’t match. For example, if you are planning to set the Required property to Yes or specify a Validation Rule property of Is Not Null on a field ...