IsEmpty() vs = "" vs = 0 in FileMaker calculations

Beginner

IsEmpty, comparison to empty string, and comparison to zero all test "emptiness" differently in FileMaker. Learn exactly what each one checks and why mixing them up causes silent bugs.

What you'll learn

What IsEmpty() checks and when it returns True vs False
Why a number field containing 0 is not empty, and a text field containing "" is
The right function to use for each type of emptiness check

IsEmpty() returns True only when a field contains absolutely nothing — no characters, no spaces, no zero — while = "" and = 0 compare the displayed value and can return unexpected results on typed fields.

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Use IsEmpty() for a true null check

IsEmpty() returns True only when the field has never been set or was explicitly cleared. A number field set to 0 is not empty — it has the value 0.

FileMaker Script

# IsEmpty returns True only if the field has no value at all
If [ IsEmpty ( Contacts::phone ) ]
  # phone has never been entered
End If

# A field containing 0 is NOT empty
Set Variable [ $x ; Value: 0 ]
If [ IsEmpty ( $x ) ]  # FALSE — $x has the value 0
  # This branch is never reached
End If

Type coercion in FileMaker: GetAsNumber, GetAsText, GetAsDate Substitute() for text replacement in FileMaker