Define the reference key
By default, reference fields store the sys_id of the record in the database.
Before you begin
Role required: personalize_dictionary
About this task
By defining a reference key, you can identify a field other than sys_id to use as the unique identifier for the reference field. The value of the reference key field, instead of the sys_id, is stored in the database for that reference field.
Procedure
Navigate to All > System Definition > Dictionary.
Open the field record (for example, resolved_by on the Incident table).
In the Reference key field, enter a field name on the referenced table (for example, email on the sys_user table).
Note: Always choose a field from the referenced table that is both required and unique.
Select Update.