Which type of key consists of multiple attributes that uniquely identify a record in a table?

Which type of key consists of multiple attributes that uniquely identify a record in a table?

• A. Foreign key
• B. Primary key
• C. Composite key
• D. Alternate key

Answer: (C)

A composite key is a type of key that consists of two or more attributes combined to uniquely identify a record in a table. In database design, a composite key is essential when no single attribute can uniquely define a record. By combining multiple attributes, the composite key ensures that each entry in the table remains distinct from others, thus maintaining data integrity. For example, in a table that records student enrollment in courses, neither the student ID nor the course ID alone may be sufficient to identify a unique record. However, the combination of both attributes—student ID and course ID—creates a composite key that uniquely identifies each enrollment record. The other types of keys serve different purposes. A primary key ensures that each record in a table is unique, but it does not necessarily have to consist of multiple attributes; it can be a single attribute as well. A foreign key is used to establish a link between two tables, referencing the primary key of another table to maintain referential integrity. An alternate key is a candidate key that is not chosen as the primary key but still can uniquely identify records in a table.

A composite key is a type of key that consists of two or more attributes combined to uniquely identify a record in a table. In database design, a composite key is essential when no single attribute can uniquely define a record. By combining multiple attributes, the composite key ensures that each entry in the table remains distinct from others, thus maintaining data integrity.

For example, in a table that records student enrollment in courses, neither the student ID nor the course ID alone may be sufficient to identify a unique record. However, the combination of both attributes—student ID and course ID—creates a composite key that uniquely identifies each enrollment record.

The other types of keys serve different purposes. A primary key ensures that each record in a table is unique, but it does not necessarily have to consist of multiple attributes; it can be a single attribute as well. A foreign key is used to establish a link between two tables, referencing the primary key of another table to maintain referential integrity. An alternate key is a candidate key that is not chosen as the primary key but still can uniquely identify records in a table.