NIELIT 2021 Dec Scientist A - Section B: 72

Question

Consider the relations :

$\text{R}_{1} \{ \text{Roll_no, Name, Grades} \}$ and $\text{R}_{2} \{ \text{Roll_no, Subject_ID, Grades} \}$

Which of the following operations cannot be performed using the above relations?

• A. Union
• B. Select
• C. Join
• D. Project

Answer 1

Select ,join ,project operation can be performed on the above relation.

Union can’t be perform on the above relation as the above two relation are not union compatible.

Two relations R and S are union compatible if they have the same number of columns and corresponding columns have the same domains.

here R1’s Name and R2’s Subject_ID domain are not same.

correct option A.