What is a composite key in database design?

What is a composite key in database design?

• A. A key made from a single column
• B. A key that consists of two or more attributes that uniquely identify a record
• C. A key that cannot be null
• D. A temporary key that is generated during database queries

Answer: (B)

A composite key is defined as a key that consists of two or more attributes that together uniquely identify a record in a database table. This means that no single attribute is sufficient on its own to uniquely distinguish a record, but when combined, these attributes form a unique identifier for each entry. The use of composite keys is particularly important in situations where an individual field might have duplicates, such as in a many-to-many relationship. By combining multiple fields, the database can enforce uniqueness and maintain data integrity. For instance, in a student-course enrollment system, a composite key could be formed by combining the student ID and the course ID, ensuring that each student-course pairing is unique. Understanding composite keys is essential for designing normalized databases and for ensuring proper relationships between tables in relational database management systems.

A composite key is defined as a key that consists of two or more attributes that together uniquely identify a record in a database table. This means that no single attribute is sufficient on its own to uniquely distinguish a record, but when combined, these attributes form a unique identifier for each entry.

The use of composite keys is particularly important in situations where an individual field might have duplicates, such as in a many-to-many relationship. By combining multiple fields, the database can enforce uniqueness and maintain data integrity. For instance, in a student-course enrollment system, a composite key could be formed by combining the student ID and the course ID, ensuring that each student-course pairing is unique.

Understanding composite keys is essential for designing normalized databases and for ensuring proper relationships between tables in relational database management systems.