Composite Key
A composite key is a database concept where two or more columns are combined to uniquely identify a row in a table, rather than using a single column. It is commonly used in relational databases when no single column has unique values, but the combination of multiple columns does. This ensures data integrity and supports complex relationships between tables.
Developers should use composite keys when designing database schemas where natural keys (like a combination of first name, last name, and birth date) or business logic requires multiple attributes to uniquely identify records. They are essential in many-to-many relationship tables (e.g., linking students and courses) and for enforcing uniqueness constraints across multiple fields, improving query performance in certain scenarios by avoiding surrogate keys.