Question

Consider the following tables R1 and R2:

R1.A1 R1.B1
------------
1      1
NULL   2
3      NULL

R2.A2 R2.B2
------------
1      1
NULL   2
3      NULL


The tuple (3, NULL, 3, NULL) appears in the answer of which of the following SQL Statements? Check all that apply

	A.	select * from R1,R2;
	B.	select * from R1,R2 where R1.A1=R2.A2;
	C.	select * from R1,R2 where R1.A1=R2.A2 and R1.B1=R2.B2;

Suppose relation R(A,B,C) has the following tuples
A B C
-----
2 3 4
5 3 4
5 6 7
3 6 4
2 3 7

and relation S(A,B,C) has the following tuples:

A B C
----
3 6 4
3 6 5
5 6 7
2 3 4

Compute the intersection of R and S. Which of the following tuples is in the result?

	A.	(2,3,5)
	B.	(3,6,4)
	C.	(3,6,5)
	D.	(3,3,7)

Answer 1

1.The tuple (3, NULL, 3, NULL) appears in the answer of which of the following SQL Statements?

Answer:-

Option A and B are correct

output to A. select * from R1,R2;

NULL   2   1   1
3   NULL   1   1
1   1   NULL   2
NULL   2   NULL   2
3   NULL   NULL   2
1   1   3   NULL
NULL   2   3   NULL
3   NULL   3   NULL

Output to B. select * from R1,R2 where R1.A1=R2.A2;

1   1   1   1
3   NULL   3   NULL

2. Compute the intersection of R and S. Which of the following tuples is in the result?

Answer:-

Option B is correct

The output of the query will be:-

(2,3,7)

(5,6,7)

(3,6,4)