In Relational Databases, a Composite Key (sometimes called "Compound Key") is a Candidate Key that is comprised of more than 1 attribute.

Example

Given a table with fields:

• student_id
• first_name
• last_name
• is_enrolled

There are two sets of Candidate Keys.

1. student_id
2. first_name, last_name

Since the Candidate Key student_id is comprised of only one attribute, it is NOT a composite key. Also, because student_id is

Since the Candidate Key first_name, last_name is comprised of more than one attribute, it is a Composite Key.

Source

Database normalization - Wikipedia

Related Notes

Candidate Key

Relational Databases