title: Microsoft Access - not using a validation code
body: <p>Under <code>PostCode</code>, I've put an input mask as well as a validation rule of '<code>Is Not Null</code>'
  <img src="https://i.stack.imgur.com/jfJpX.png" alt="Valdiation rules" />
  The input mask is working fine. However, the validation rule isn't working as it allows the postcode to be null.</p>
  <p>Is there a way to fix this?</p>