ERD:

Scenario:

The above ERD represents the details of a simple course database which records the course registration details of students. The course entity has a unique identifier CourseNum and the Registration entity is allocated a partial key. The mode represents the mode of registration: online or on-campus. A student may have more than one phone number.

Semantic Rules:

1. Each course may have many registrations.
2. Many registrations are recorded for each course.
2. Each student may register only once.
2. Each student can have multiple registrations.

Question: Which of the following relation is a result of correcting the multivalued attribute in the Course Registration database?

Question

ERD:

Scenario:

The above ERD represents the details of a simple course database which records the course registration details of students. The course entity has a unique identifier CourseNum and the Registration entity is allocated a partial key. The mode represents the mode of registration: online or on-campus. A student may have more than one phone number.

Semantic Rules:

1. Each course may have many registrations.
2. Many registrations are recorded for each course.
2. Each student may register only once.
2. Each student can have multiple registrations.

Question: Which of the following relation is a result of correcting the multivalued attribute in the Course Registration database?

BlackTom AI · Accepted Answer

Question restatement: The ERD describes a Course Registration database where a student may have multiple phone numbers, and the multivalued attribute is Phone under the Registration/Student area. The task asks which relation results from correcting the multivalued attribute in the Course Registration database.

Option A: StudentContact(StudentNum,Phone)
- Analysis: This design creates a separate relation where each row associates one StudentNum with one Phone. This correctly handles the multivalued Phone attribute by normalizing it into a separate relation, preserving the one-to-many relationship between a student and their phone numbers. This approach aligns with normalization principles (eliminating multivalued attributes by splitting into a separate relation).

Option B: StudentContact(StudentNum,Email1,Email2)
- Analysis: This suggests two email attributes for a student within a single row. It does not address the stated multivalued attribute (Phone) and instead implies a fixed set of two emails, which does not generalize to any number of emails. It also confuses the identified multivalued attribute handling with emails, which are not described as multivalued in the scenario. This is not an appropriate normalization for a multivalued phone attribute.

Option C: StudentContact(StudentNum,Email)
- Analysis: This relation captures a single Email per StudentNum. If a student truly can have multiple contact methods (emails) in the real design, this would fail to represent multiple emails per student. The original problem emphasizes multiple phone numbers, not multiple emails, so this option addresses a different attribute and would not fix the multivalued Phone issue.

Option D: StudentContact(StudentNum,Phone1, Phone2)
- Analysis: This uses fixed multiple columns for phones, which still imposes a fixed limit on how many phone numbers a student can have and violates the goal of a clean multivalued attribute normalization. It’s essentially a workaround that caps the number of possible phone numbers and doesn’t scale well, making it an inferior solution to the proper separate relation approach.

Overall, the best design to correct the multivalued attribute is to move the phone values into their own relation, leaving a single Phone attribute associated with each StudentNum in the new relation. The other options either mishandle the multivalued aspect, address the wrong attribute, or impose artificial limits on the number of phones a student can have.

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