Gate CS-2018 Question Paper With Solutions

Q. 29 Consider the following two tables and four queries in SQL.

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 B 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 B 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 the other three queries?

(A) Query 1

(B) Query 2

(C) Query 3

(D) Query 4

Answer: (D)

Explanation: