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Question

When creating an associative entity ENROLL, which is optional on both ends but connects STUDENTs to CLASSes, what would be true about ENROLL if its composite PK is made up of the PKs of STUDENT and CLASS?

The choices are:

a. have a mandatory relationship with STUDENT and CLASS

b. be a regular entity

c. have strong connections with STUDENT and CLASS

d. be a strong entity

Answer 1

The correct answer is:

d. be a strong entity

When the composite primary key (PK) of the ENROLL table is made up of the PKs of STUDENT and CLASS, it implies that ENROLL is strongly connected to both STUDENT and CLASS. This means that every enrollment record will have both a student ID and a class ID, and there is a unique combination of student and class IDs for each enrollment.

In other words, the composite PK is a strong relationship, meaning that if one entity is not present, the other entity cannot be present. This is an example of a strong entity in the context of database design.

The other options are incorrect because:

a. A mandatory relationship is not explicitly stated in the question. While it's true that ENROLL is an associative entity, it's not necessarily mandatory.

b. Being a regular entity is not necessarily true. A regular entity is typically a simple association between two tables, whereas ENROLL is a composite entity that has two related tables (STUDENT and CLASS).

c. Having strong connections with STUDENT and CLASS is not necessarily true. While it's true that the composite PK is a strong relationship, ENROLL can also be a weak entity if not properly defined.