How do you map a many-to-many relationship to a relational schema?

• A. Create a junction (bridge) table containing the primary keys of the related tables as foreign keys (and possibly additional attributes).
• B. Store the pair of keys as a single combined key on one table.
• C. Embed one table's foreign key into the other table.
• D. Use a view to simulate the relationship.

Answer: (A)

To map a many-to-many relationship in a relational schema, you create an associative (bridge) table that links the two entities. This bridge table holds the primary keys of both related tables as foreign keys, and those keys typically form a composite primary key. The bridge can also carry attributes that describe the relationship itself, such as a timestamp or a specific role.

For example, between students and courses, an Enrollment table would have student_id and course_id as foreign keys pointing to Students and Courses. Each row represents one student taking one course, and you can add extra fields like grade or enrollment_date if needed.

This approach is preferred because it cleanly represents multiple associations without duplicating data, maintains normalization, and allows the relationship to carry its own attributes. Other options don’t fit: embedding one table’s foreign key into the other creates a one-to-many link rather than many-to-many; combining keys into a single key on one table ties the relationship to that table and complicates constraints; and using a view doesn’t enforce or store the actual relationship in the data model.