GATE 2018 Previous Year Paper Solution Question 12 – Computer Science

In this video question which was asked in the exam of GATE 2018 is discussed.

Question :- Consider the following two tables and four queries in SQL.
Book (isbn, bname), Stock (isbn, copies)

Query 1 :- SELECT B.isbn, S.copies
FROM Book B INNER JOIN Stock S
ON B.isbn = S.isbn ;

Query 2 :- SELECT B.isbn, S.copies
FROM Book B LEFT OUTER JOIN Stock S
ON B.isbn = S.isbn;

Query 3 :- SELECT B.isbn, S.copies
FROM Book B RIGHT OUTER JOIN Stock S
ON B.isbn = S.isbn;

Query 4 :- SELECT B.isbn, S.copies
FROM Book B FULL OUTER JOIN Stock S
ON B.isbn = S.isbn;

Which one of the queries above is certain to have an output that is a superset of the outputs of other three queries ?

A. Query 1
B. Query 2
C. Query 3
D. Query 4

Solution is explained in the video.