Database-Management-System

Question 439

In relational database management, which of the following is/are property/properties of candidate key?
P:Uniqueness
Q: Irreducibility

A	P only
B	Q only
C	Both P and Q
D	Neither P nor Q

Database-Management-SystemCandidate-keyUGC NET June-2019 CS Paper-2

Question 439 Explanation:

Let K be a subset of the heading of relvar R. Then K is a candidate key (or just key for short) for R if and only if it possesses both of the following properties:
Uniqueness: No valid value for R contains two distinct tuples with the same value for K.
Irreducibility: No proper subset of K has the uniqueness property.

Correct Answer: C

Question 439 Explanation:

Let K be a subset of the heading of relvar R. Then K is a candidate key (or just key for short) for R if and only if it possesses both of the following properties:
Uniqueness: No valid value for R contains two distinct tuples with the same value for K.
Irreducibility: No proper subset of K has the uniqueness property.