6.8

Consider a relation such as sec_course, generated from a many-to-one relationship set sec_course. Do the primary and foreign key constraints created on the relation enforce the many-to-one cardinality constraint? Explain why.

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In this example, the primary key of section consists of the attributes (course_id, sec_id, semester, year) which would also be the primary key of sec_course, while course_id is a foreign key from sec_course referencing course. These constraints ensure that a particular section can only correspond to one course, and thus the many-to-one cardinality constraint is enforced.

However, these constaints cannot enforce a total participation constraint, since a course or a section may not participate in the sec_course relationship.