Lookup fields vs live related fields

Beginner

Understand the difference between a lookup field (which copies a value at a point in time) and a live related field (which always reflects the current related value), and when to use each.

What you'll learn

What a lookup does and when the copy happens
How a live related field differs from a lookup in behavior
When to use a lookup vs a live related field in practice

A lookup copies data from a related record into the current record at a specific moment; a live related field always reads the current value from the related record — the choice between them depends on whether the value should be frozen or stay current.

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Set up a lookup field

A lookup is a regular field with a "Looked-up value" auto-enter option. It copies the value from a related field when the match field changes. After copying, the value is independent of the source.

FileMaker Script

# Field: Orders::UnitPrice
# Auto-enter: Looked-up value
# Lookup from related record: Products (via Orders → Products relationship)
# Copy value from field: Products::Price
# If no related record: leave field blank

# When Orders::ProductID is set or changed:
# → FileMaker copies Products::Price into Orders::UnitPrice
# → Future changes to Products::Price do NOT affect Orders::UnitPrice

Allow creation of records via a relationship The Anchor-Buoy methodology for the Relationships Graph