Database-Management-System

Question 472

Given two relations R1(A, B) and R2(C, D), the result of following query

Select distinct A, B

from R1, R2

is guaranteed to be same as R1 provided one of the following condition is satisfied.

A	R1 has no duplicates and R2 is empty.
B	R1 has no duplicates and R2 is non – empty.
C	Both R1 and R2 have no duplicates.
D	R2 has no duplicates and R1 is non – empty.

Database-Management-SystemSQLUGC NET CS 2017 Nov- paper-3

Question 472 Explanation:

Option(A): Cartesian product with a empty table will result in zero tuple because we can’t have any ordered pair with a empty table. Hence option(A) is incorrect option.
Option(B):

Correct Answer: B

Question 472 Explanation:

Option(A): Cartesian product with a empty table will result in zero tuple because we can’t have any ordered pair with a empty table. Hence option(A) is incorrect option.
Option(B):