1
GATE CSE 2007
MCQ (Single Correct Answer)
+2
-0.6
Consider the following schedules involving two transactions. Which one of the following statements is TRUE?

S1: r1(X); r1(Y); r2(Y); r2(X); w2(Y); w1(X);

S2: r1(X); r2(X); r2(Y); w2(Y); r1(Y); w1(X);

A
Both S1 and S2 are conflict serializable.
B
S1 is conflict serializable and S2 is not conflict serializable.
C
S1 is not conflict serializable and S2 is conflict serializable.
D
Both S1 and S2 are not conflict serializable.
2
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))
3
GATE CSE 2007
MCQ (Single Correct Answer)
+2
-0.6

Consider the relation employee(name, sex, supervisorName) with name as the key, supervisorName gives the name of the supervisor of the employee under consideration. What does the following Tuple Relational Calculus query produce?

$$\eqalign{ & \{ e.name\,|\,employee(e) \wedge \cr & (\forall x)[\neg employee(x) \vee \cr & x.\sup ervisorName \ne e.name\, \vee \cr & x.sex = 'male']\} \cr} $$
A
Names of employees with a male supervisor.
B
Names of employees with no immediate male subordinates.
C
Names of employees with no immediate female subordinates.
D
Names of employees with a female supervisor.
4
GATE CSE 2007
MCQ (Single Correct Answer)
+2
-0.6
Consider a selection of the form σA ≤ 100(r), where r is a relation with 1000 tuples. Assume that the attribute values for A among the tuples are uniformly distributed in the interval [ 0, 500 ]. Which one of the following options is the best estimate of the number of tuples returned by the given selection query?
A
50
B
100
C
150
D
200
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