1
GATE CSE 2012
MCQ (Single Correct Answer)
+2
-0.6
Consider the following transactions with data items P and Q initialized to zero:
T1 : read (P) ; 
     read (Q) ; 
     if P = 0 then Q : = Q + 1 ; 
     write (Q). 
T2 : read (Q) ; 
     read (P) 
     if Q = 0 then P : = P + 1 ; 
     write (P).
Any non-serial interleaving of T1 and T2 for concurrent execution leads to
A
a serializable schedule
B
a schedule that is not conflict serializable
C
a conflict serializable schedule
D
a schedule for which precedence graph cannot be drawn
2
GATE CSE 2010
MCQ (Single Correct Answer)
+2
-0.6
Consider the following schedule for transactions T1, T2 and T3: GATE CSE 2010 Database Management System - Transactions and Concurrency Question 17 English Which one of the schedules below is the correct serialization of the above?
A
$$T1 \to T3 \to T2$$
B
$$T2 \to T1 \to T3$$
C
$$T2 \to T3 \to T1$$
D
$$T3 \to T1 \to T2$$
3
GATE CSE 2009
MCQ (Single Correct Answer)
+2
-0.6
Consider two transactions T1 and T2 and four schedules S1, S2, S3, S4 of T1 and T2 as given below:

T1: R1[ x ] W1[ x ] W1[ y ]
T2: R2[ x ] R2[ y ] W2[ y ]
S1: R1[ x ] R2[ x ] R2[ y ] W1[ x ] W1[ y ] W2[ y ]
S2: R1[ x ] R2[ x ] R2[ y ] W1[ x ] W2[ y ] W1[ y ]
S3: R1[ x ] W1[ x ] R2[ x ] W1[ y ] R2[ y ] W2[ y ]
S4: R2[ x ] R2[ y ] R1[ x ] W1[ x ] W1[ y ] W2[ y ]

Which of the above schedules are conflict-serializable?
A
S1 and S2
B
S2 and S3
C
S3 only
D
S4 only
4
GATE CSE 2009
MCQ (Single Correct Answer)
+2
-0.6
Let R and S be relational schemes such that R = { a, b, c } and S = { c }. Now consider the following queries on the database:

I. $$\pi_{R-S}(r) - \pi_{R-S} \left (\pi_{R-S} (r) \times s - \pi_{R-S,S}(r)\right )$$

II. $$\left\{t \mid t \in \pi_{R-S} (r) \wedge \forall u \in s \left(\exists v \in r \left(u = v[S] \wedge t = v\left[R-S\right]\right )\right )\right\}$$

III.$$\left\{t \mid t \in \pi_{R-S} (r) \wedge \forall v \in r \left(\exists u \in s \left(u = v[S] \wedge t = v\left[R-S\right]\right )\right ) \right\}$$

IV. Select R.a, R.b
    From R, S
    Where R.c = S.c
Which of the above queries are equivalent?
A
I and II
B
I and III
C
II and IV
D
III and IV
GATE CSE Subjects
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Graduate Aptitude Test in Engineering
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CBSE
Class 12