What feature does a compound key provide in data management?

What feature does a compound key provide in data management?

• A. It simplifies the data model
• B. It uniquely identifies an entity instance
• C. It links multiple entities
• D. It indicates a relationship type

Answer: (B)

A compound key provides the crucial feature of uniquely identifying an entity instance in a database. By combining multiple attributes, a compound key ensures that each record in a table can be distinguished from every other record, even if the individual attributes might not be unique on their own. This is particularly important in scenarios where a single attribute cannot reliably provide uniqueness. For example, in a database table that stores information about student enrollments in courses, the combination of student ID and course ID could serve as a compound key. Since either attribute alone (student ID or course ID) may not be unique across records, their combination guarantees that each enrollment instance is uniquely identifiable. Other options, while they touch on areas relevant to data management, do not define the primary function of a compound key. Simplifying the data model or indicating relationships can be influenced by keys, but they are not fundamental characteristics as the role of uniquely identifying entity instances is. Furthermore, linking entities typically involves foreign keys or other data structure designs rather than solely relying on compound keys. Thus, the distinctive role of a compound key lies in its ability to provide unique identification for entity instances.

A compound key provides the crucial feature of uniquely identifying an entity instance in a database. By combining multiple attributes, a compound key ensures that each record in a table can be distinguished from every other record, even if the individual attributes might not be unique on their own. This is particularly important in scenarios where a single attribute cannot reliably provide uniqueness.

For example, in a database table that stores information about student enrollments in courses, the combination of student ID and course ID could serve as a compound key. Since either attribute alone (student ID or course ID) may not be unique across records, their combination guarantees that each enrollment instance is uniquely identifiable.

Other options, while they touch on areas relevant to data management, do not define the primary function of a compound key. Simplifying the data model or indicating relationships can be influenced by keys, but they are not fundamental characteristics as the role of uniquely identifying entity instances is. Furthermore, linking entities typically involves foreign keys or other data structure designs rather than solely relying on compound keys. Thus, the distinctive role of a compound key lies in its ability to provide unique identification for entity instances.