Question

Which relation is created by placing the primary key of either entity in the relation for the other entity or by doing this for both entities?

A) Binary 1:N relationship
B) Unary 1:1 relationship
C) Weak entity
D) Associative entity with additional key

Answer 1

An Associative entity with an additional key is created in many-to-many relationships and includes the primary keys from the linked entities as foreign keys, plus additional relationship-specific attributes.

Step-by-step explanation:

The type of relationship described in the question is known as an Associative entity with an additional key. This occurs in many-to-many (M:N) relationships where a separate entity, known as an associative entity or join table, is used to store information about the associations between the two entities. This associative entity will contain foreign keys that are the primary keys from the two entities being linked, along with potentially other attributes that are relevant to the relationship.

For example, consider a scenario with two entities: 'Students' and 'Courses'. The relationship between these entities is many-to-many as a student can enroll in multiple courses, and a course can have many students. In this case, an associative entity such as 'Enrollments' would be created. It would include the primary keys from both 'Students' and 'Courses' (now acting as foreign keys) along with additional attributes like enrollment dates or grades.