2007 Microsoft® Office System Step by Step, Second Edition

Restricting Data by Using Validation Rules

A validation rule is an expression that can precisely define the information that will be accepted in one or several fields in a record. You might use a validation rule in a field containing the date an employee was hired to prevent a date in the future from being entered. Or if you make deliveries to only certain local areas, you could use a validation rule on the phone field or ZIP code field to refuse entries from other areas.

You can type validation rules in by hand, or you can use the Expression Builder to create them. At the field level, Access uses the rule to test an entry when you attempt to leave the field. At the table level, Access uses the rule to test the content of several fields when you ...