An Entity Identifier must have its Data Type set to what?

An Entity Identifier, which serves as the unique key for a record in a database, is designed to reference individual entries distinctly. It is essential for the primary key of an entity to be a single attribute, as this upholds the integrity of the records and ensures that each entry can be uniquely identified without any ambiguity.

Using just a single attribute simplifies operations such as lookups, relationships with other entities, and maintaining data integrity. It prevents the complexity that could arise from composite keys, which involve multiple attributes and can lead to challenges in data retrieval and consistency.

In this context, the other options provide different data types or configurations that are not valid for setting a singular Identifier for an entity. For instance, while long integers and auto numbers are specific data types that could be used in the context of identifiers, they do not address the requirement for the identifier to be a single unique attribute. Options like "automatically created" pertain more to the behavior of the identifier rather than defining how it should be structured in terms of multiple or single attributes. Thus, the requirement for an Entity Identifier to be a single attribute underscores its role in uniquely defining entities within the database structure.