What is the purpose of a foreign key in Contact Builder?

The purpose of a foreign key in Contact Builder is to connect data between different sources in a relational database. In database management, a foreign key is a column or a set of columns in one table that uniquely identifies a row of another table or the same table. By using foreign keys, you can establish relationships between data extensions, allowing for more complex and interrelated data management within the system. This makes it possible to pull in related data and analyze it collectively, thus enriching your marketing efforts with a more comprehensive view of customer interactions and behaviors.

While uniquely identifying data points is important, that function is primarily served by primary keys, which are distinct from foreign keys. Foreign keys instead reference these primary keys in other tables to create links. Similarly, serving as a primary key is not the function of a foreign key, as its role is to reference another table rather than being the main identifier in its own right. Unlocking external data is also not directly associated with the primary purpose of a foreign key, as foreign keys are more about maintaining relationships within the data structure rather than accessing external sources.