Composite Keys in SQL

Composite Keys in SQL — a practical guide to SQL composite key with clear examples you can reuse in real projects.

SQL Tutorial Series (10/100). Prefer one article? Read the complete SQL tutorial.

Short description

Common in junction tables for many-to-many relationships.

Composite PK

CREATE TABLE course_user (
  course_id INT UNSIGNED NOT NULL,
  user_id INT UNSIGNED NOT NULL,
  PRIMARY KEY (course_id, user_id)
);