Primary keys and foreign keys: UUID vs serial number

Beginner

Choose the right primary key strategy for your FileMaker tables — and understand why UUID (Get(UUID)) is safer than an auto-incrementing serial number.

What you'll learn

The difference between a serial number and a UUID as a primary key
How to set up a Get(UUID) auto-enter calculation for a primary key
How foreign keys reference primary keys across tables

Every table needs a primary key that uniquely identifies each record, and the choice of key type has lasting consequences for data integrity in multi-user and multi-file environments.

1/3

Set up a UUID primary key with auto-enter

Create a text field named "id" (or "CustomerID", etc.). In Field Options > Auto-Enter, select "Calculated value" and enter Get(UUID). Uncheck "Do not replace existing value" so the calculation fires only on new records.

FileMaker Script

# Field: Customers::CustomerID
# Type: Text
# Auto-Enter: Calculated value
#   Calculation: Get ( UUID )
# [ ] Do not replace existing value of field (if any)  ← leave UNCHECKED
#     so the UUID is set when the record is created

# Result: each new Customers record gets a value like:
# "7A4B2C91-3E5F-4A12-89DE-BC01234567FA"

Relationship operators: =, ≠, <, >, ≤, ≥, and range How layout context determines related records