The Customer ID field is the match field in the relationship between the two tables. In the Customers table, the Customer ID field is set to auto-enter a serial number, giving each record in the Customers table a unique ID number. In the Contacts table, the Customer ID is a simple number field, and no auto-entry options are set.
In the Edit Relationship dialog box, the Allow creation of records in this table via this relationship option is enabled. This means that you will be able to enter a phone number in an empty
portal row, and FileMaker Pro will automatically create a related record for that phone number. Also, the
Delete related records in this table when a record is deleted in the other table option is enabled, because there is no reason to retain old phone numbers if the matching contact record has been deleted.
Because the relationship is defined to allow the creation of related records in the Contacts table, the Customer ID number from a Customers record will be automatically inserted in the Customer ID field in the Contacts table in each new related record. This allows many records in the Contacts table to be related to a single record in the Customers table.
Finally, a portal is added to the Contacts table on the Customer layout. When you enter a phone number or an email address in an empty portal row in the Customers table, FileMaker Pro creates a related record for that phone number or email address in the Contacts table.