Validation without requiring entry
I created a fresh new data bridge backend for a database table a few months back. The project has sat until now. I was doing some final testing and I'm having an issue with form validation. It would appear that all of my form fields that I'm using validation for are requiring an entry on the insert page. I want to validate things like phone numbers for proper format IF there is an entry, but I don't want to REQUIRE an entry. It's fine if the field is left blank.
What determines whether the validation requires entry, vs checking for valid format only if there is an entry?