A product can be supplied by many suppliers with each offering different price. What is the correct ER design?

An associative entity Product_Supplier is required because the price depends on the pair (Product, Supplier), and must be stored as a relationship attribute.

In a university ER model, Section is part of Course and cannot exist independently. What is Section?

Section is a Weak Entity because it depends on the existence of a Course and is identified using the Course key with its own partial key.

A company wants to store that an employee mentors another employee. What type of relationship is this?

It is a Recursive Relationship where an entity type participates in a relationship with itself, such as Employee mentoring another Employee.

If two entities share a relationship that contains attributes, the relationship should be represented as:

Such a relationship should be converted into an Associative Entity so that relationship attributes can be stored.

Computer Science and Engineering - Tutorials, Notes, MCQs, Questions and Answers: Top 50 ER Modeling MCQs with Answers & Detailed Explanations (2025 Update)

Q: In an ER model for a hospital, each patient can have multiple allergies. How should allergies be represented?

Allergies should be represented as a multivalued attribute since a patient may have more than one allergy, or alternatively as a separate related table in logical design.

Q: If an entity type has a key attribute that consists of multiple attributes, what is the key called?

It is called a Composite Key, which contains two or more attributes that together uniquely identify entity instances.

Q: Total participation of an entity in a relationship means:

Total participation means that every instance of an entity must participate in the relationship (mandatory participation).

Q: A derived attribute is one that:

A derived attribute is computed from other stored attributes. For example, Age can be derived from Date of Birth.

Q: When converting an ER model to relations, a many-to-many relationship becomes:

A separate table containing foreign keys from both related entities, representing the many-to-many relationship.

Q: A specialization where an instance may belong to multiple subtypes simultaneously is called:

It is called Overlapping Specialization, where an entity may belong to more than one subtype at the same time.

Thursday, November 27, 2025

Top 50 ER Modeling MCQs with Answers & Detailed Explanations (2025 Update) - SET 01

✔ Scroll down and test yourself — answers are hidden under the “View Answer” button.

1. In an ER model for a hospital, each patient can have multiple allergies. How should "allergies" be represented?

A. As a simple attribute of Patient
B. As a multivalued attribute
C. As a weak entity
D. As a derived attribute

Answer: B
Explanation:

Since a patient can have more than one allergy, it must be modeled as a multivalued attribute or as a separate related table in logical design.

2. A product can be supplied by many suppliers, and each supplier may offer a different price. What is the correct ER design?

A. Store price in Product
B. Store price in Supplier
C. Use a ternary entity
D. Create an associative entity Product_Supplier

Answer: D
Explanation:

The price depends on the pair (Product, Supplier), so an associative entity is required to store relationship attributes like price.

3. If an entity type has a key attribute that consists of multiple attributes, that key is called:

A. Prime key
B. Composite key
C. Partial key
D. Weak key

Answer: B
Explanation:

A composite key contains two or more attributes that uniquely identify entity instances.

4. In a university ER model, “Section” is part of a “Course” and cannot exist independently. What is Section?

A. Strong entity
B. Composite attribute
C. Weak entity
D. Multivalued attribute