What is required in a data extension for an add or update operation?

In the context of a data extension within Salesforce Marketing Cloud, for an add or update operation, a primary key is essential. The primary key uniquely identifies each record within the data extension, ensuring that when records are added or updated, the system can accurately determine whether to create a new entry or modify an existing one.

When an operation is executed in Marketing Cloud that involves adding or updating data, the system references the primary key to find the correct record. If the primary key matches an existing record, the system will proceed with an update, incorporating any new information provided. If there is no match, a new record will be created.

While Subscriber Key and Email Address can play vital roles in identifying a subscriber within certain contexts, they do not inherently fulfill the requirement of a primary key in a data extension. Similarly, Secondary Key serves as an additional identifier but is not mandatory for the add or update operations. Having the primary key allows for precise data management, ensuring data integrity and accuracy in the system.