Northern Trail Outfitters wants to add new data extensions containing customer purchases to their Marketing...

In Salesforce Marketing Cloud, linking new data extensions in Data Designer to existing contact records requires using a "Unique Contact Identifier." This identifier ensures that each record in the data extension can be uniquely associated with a corresponding record in the contact database, thereby enabling accurate targeting, segmentation, and personalization. It is vital that this identifier is consistently used across data extensions to maintain data integrity and proper linkages.