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Data & Analytics · Intermediate

Many-to-Many Relationship (Database) (M:N)

A relationship where many rows in one table relate to many rows in another; it is resolved with a junction table.

Definition

Relational databases cannot implement M:N directly, so designers create an associative (junction) table containing foreign keys to both sides, which turns the relationship into two one-to-many relationships. Power BI supports many-to-many cardinality but warns about ambiguity and performance.

Example

Students and Courses connected through an Enrollments table.

Exam tip

If asked how to physically implement an M:N relationship, answer 'add a junction/bridge table'.

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