1
GATE CSE 2011
MCQ (Single Correct Answer)
+2
-0.6
Consider a relational table r with sufficient number of records, having attributes A1, A2,....., An and let 1 $$ \le $$ p $$ \le $$ n. Two queries Q1 and Q2 are given below.

$$Q1: \pi_{A_1, \dots ,A_p} \left(\sigma_{A_p=c}\left(r\right)\right)$$ where is a constant

$$Q2: \pi_{A_1, \dots ,A_p} \left(\sigma_{c_1 \leq A_p \leq c_2}\left(r\right)\right)$$ where c1 and c2 are constants

The database can be configured to do ordered indexing on Ap or hashing on Ap. Which of the following statements is TRUE?

A
Ordered indexing will always outperform hashing for both queries
B
Hashing will always outperform ordered indexing for both queries
C
Hashing will outperform ordered indexing on Q1, but not on Q2
D
Hashing will outperform ordered indexing on Q2, but not on Q1
2
GATE CSE 2010
MCQ (Single Correct Answer)
+2
-0.6
The following functional dependencies hold for relations R(A, B, C) and S(B, D, E): $$$\eqalign{ & B \to A \cr & A \to C \cr} $$$

The relation R contains 200 tuples and the relation S contains 100 tuples. What is the maximum number of tuples possible in the natural join R $$\Join$$ S?

A
100
B
200
C
300
D
2000
3
GATE CSE 2008
MCQ (Single Correct Answer)
+2
-0.6
Let R and S be two relations with the following schema

R (P, Q, R1, R2, R3)

S (P, Q, S1, S2)

Where {P, Q} is the key for both schemas. Which of the following queries are equivalent?
I. $$\Pi_P \left(R \bowtie S\right)$$
II. $$\Pi_P \left(R\right) \bowtie \Pi_P\left(S\right)$$
III. $$\Pi_P \left(\Pi_{P, Q} \left(R\right) \cap \Pi_{P,Q} \left(S\right) \right)$$
IV. $$\Pi_P \left(\Pi_{P, Q} \left(R\right) - \left(\Pi_{P,Q} \left(R\right) - \Pi_{P,Q} \left(S\right)\right)\right)$$
A
Only I and II
B
Only I and III
C
Only I, II and III
D
Only I, III and IV
4
GATE CSE 2007
MCQ (Single Correct Answer)
+2
-0.6
Consider the following relation schemas :

b-Schema = (b-name, b-city, assets)
a-Schema = (a-num, b-name, bal)
d-Schema = (c-name, a-number)

Let branch, account and depositor be respectively instances of the above schemas. Assume that account and depositor relations are much bigger than the branch relation.

Consider the following query:
Пc-nameb-city = “Agra” ⋀ bal < 0 (branch $$ \Join $$ (account $$ \Join $$ depositor))

Which one of the following queries is the most efficient version of the above query ?

A
Пc-namebal < 0b-city = “Agra” branch $$ \Join $$ account) $$ \Join $$ depositor)
B
Пc-nameb-city = “Agra”branch $$ \Join $$ (σbal < 0 account $$ \Join $$ depositor))
C
Пc-nameb-city = “Agra” branch $$ \Join $$ σb-city = “Agra” ⋀ bal < 0 account) $$ \Join $$ depositor)
D
Пc-nameb-city = “Agra” ⋀ bal < 0 account $$ \Join $$ depositor))
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