Question

Consider the ER model:
E1 (A11, A12, A13)
E2 (A21, A22, A23)
Where:
- A21 is the key of E2
- A22 is a multivalued attribute
- R12 is a many-to-many relationship between E1 and E2
Find the minimum number of relations required to convert this ER model into tables.

Hint:

In ER to Relational mapping:
Each strong entity → 1 relation
Each multivalued attribute → 1 separate relation
Each many-to-many relationship → 1 separate relation

Answer 1

Correct Answer: 4

Step 1: Convert Strong Entities.
Each strong entity requires one separate relation.
So,
1 relation for E1
1 relation for E2
Total so far = 2 relations.
Step 2: Handle Multivalued Attribute.
A22 is a multivalued attribute of E2.
Each multivalued attribute requires a separate relation.
So,
1 additional relation for A22.
Total so far = 3 relations.
Step 3: Handle Many-to-Many Relationship.
A many-to-many relationship always requires a separate relation.
So,
1 relation for R12.
Total relations = 4.
Final Answer: \[ \boxed{4} \]