Creating associations to relate record definitions
Creating associations to relate record definitions is the second step to creating additional custom fields for the different record views within the Portfolio Management application.
Associate the extension record, that is, Portfolio - Extended in a one-to-one mapping with the original record, Portfolio. The association can be named as “Portfolio has one Portfolio Extension”. For information about how to create record associations, see Creating record associations.
The following screenshot displays the record association:

After you create the record association, an association field is added to the Portfolio - Extended record definition. The extension record should now have the ID of the original record as a foreign key.
The name of the association field is the value that you put in the Role of First Record field while creating the record association. In the Portfolio record definition, when you enter Portfolio in the Role of First Record field, a Portfolio_ID field is created automatically. This PORTFOLIO_ID field is the association field.