1
GATE CSE 2012
MCQ (Single Correct Answer)
+1
-0.3
Which of the following statements are TRUE about an SQL query?

P: An SQL query can contain a HAVING clause even if it does not have a GROUP BY clause
Q: An SQL query can contain a HAVING clause only if it has a GROUP BY clause
R: All attributes used in the GROUP BY clause must appear in the SELECT clause
S: Not all attributes used in the GROUP BY clause need to appear in the SELECT clause

A
P and R
B
P and S
C
Q and R
D
Q and S
2
GATE CSE 2012
MCQ (Single Correct Answer)
+2
-0.6
Suppose R1 (A, B) and R2 (C, D) are two relation schemas. Let r1 and r2 be the corresponding relation instances. B is a foreign key that refers to C in R2. If data in r1 and r2 satisfy referential integrity constraints, which of the following is ALWAYS TRUE?
A
$$\prod_{B}(r_{1})- \prod _{C}(r_{2})= \varnothing$$
B
$$\prod_{C}(r_{2})- \prod _{B}(r_{1})= \varnothing$$
C
$$\prod_{B}(r_{1}) = \prod _{C}(r_{2})$$
D
$$\prod_{B}(r_{1}) - \prod _{C}(r_{2}) \neq \varnothing$$
3
GATE CSE 2012
MCQ (Single Correct Answer)
+2
-0.6
Consider the following relations A, B and C:
A
ID Name Age
12 Arun 60
15 Shreya 24
99 Rohit 11

B
ID Name Age
15 Shreya 24
25 Hari 40
98 Rohit 20
99 Rohit 11

C
ID Phone Area
10 2200 02
99 2100 01

How many tuples does the result of the following SQL query contain?

SELECT A.Id 
FROM A 
WHERE A.Age > ALL (SELECT B.Age 
                   FROM B 
                   WHERE B.Name = 'Arun')
A
4
B
3
C
0
D
1
4
GATE CSE 2012
MCQ (Single Correct Answer)
+2
-0.6
Consider the following relations A, B and C:
A
ID Name Age
12 Arun 60
15 Shreya 24
99 Rohit 11

B
ID Name Age
15 Shreya 24
25 Hari 40
98 Rohit 20
99 Rohit 11

C
ID Phone Area
10 2200 02
99 2100 01

How many tuples does the result of the following relational algebra expression contain? Assume that the schema of A ∪ B is the same as that of A. $$(A\cup B)\bowtie _{A.Id > 40 \vee C.Id < 15} C$$

A
7
B
4
C
5
D
9
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