Many-to-many relationships require a junction/bridge table. Cannot directly link tables with foreign keys. Junction table contains foreign keys to both entities.

Junction table stores relationships between two entities. Each row represents one relationship. Query requires two joins: from entity A to junction, junction to entity B.

Many-to-many relationships are fundamental to normalized databases. Understanding junction tables is essential for modeling real-world relationships. Every e-commerce, LMS, and enterprise system uses them.

Students enroll in multiple courses, courses have multiple students. Products belong to multiple categories. Users have multiple roles. Orders contain multiple products. Every complex system has many-to-many relationships.