ER-Model

Question 28

Let M and N be two entities in an E-R diagram with simple single value attributes.
R ₁ and R₂ are two relationship between M and N, where as
R ₁ is one-to-many and R ₂ is many-to-many.
The minimum number of tables required to represent M, N, R ₁ and R₂ in the relational model are _______.

A	4
B	6
C	7
D	3

Database-Management-SystemER-ModelUGC NET CS 2017 Jan -paper-2

Question 28 Explanation:

R ₁ and R₂ two relationships between M and N
R ₁ is one to many.
R ₂ is many to many.
→ M and N have separate table because they need to store multiple values.
→ R ₂ also have separate table by considering Primary keys M and N as foreign keys.
→ R ₁ is converted to many side table i.e., N as Primary key and M as Foreign key.
So, totally we need 3 tables to store the value.

Correct Answer: D

Question 28 Explanation:

R ₁ and R₂ two relationships between M and N
R ₁ is one to many.
R ₂ is many to many.
→ M and N have separate table because they need to store multiple values.
→ R ₂ also have separate table by considering Primary keys M and N as foreign keys.
→ R ₁ is converted to many side table i.e., N as Primary key and M as Foreign key.
So, totally we need 3 tables to store the value.