1
GATE CSE 2014 Set 2
Numerical
+1
-0
The maximum number of superkeys for the relation schema $$R(E, F, G, H)$$ with $$E$$ as key is ______.
Your input ____
2
GATE CSE 2014 Set 2
MCQ (Single Correct Answer)
+2
-0.6
SQL allows duplicate tuples in relations, and correspondingly defines the multiplicity of tuples in the result of joins. Which one of the following queries always gives the same answer as the nested query shown below:
Select * from R where a in (select S.a from S)
A
Select R.* from R, S where R.a = S.a
B
Select distinct R.* from R, S where R.a = S.a
C
Select R.* from R, (select distinct a from S) as S1 where R.a = S1.a
D
Select R.* from R, S where R.a = S.a and is unique R
3
GATE CSE 2014 Set 2
MCQ (Single Correct Answer)
+2
-0.6
Consider a join (relation algebra) between relations r(R)and s(S) using the nested loop method. There are 3 buffers each of size equal to disk block size, out of which one buffer is reserved for intermediate results. Assuming size(r(R)) < size(s(S)), the join will have fewer number of disk block accesses if
A
relation r(R) is in the outer loop.
B
relation s(S) is in the outer loop.
C
join selection factor between r(R) and s(S) is more than 0.5.
D
join selection factor between r(R) and s(S) is less than 0.5.
4
GATE CSE 2014 Set 2
MCQ (Single Correct Answer)
+2
-0.6
Consider the following schedule S of transactions T1, T2, T3, T4: GATE CSE 2014 Set 2 Database Management System - Transactions and Concurrency Question 17 English
A
S is conflict-serializable but not recoverable
B
S is not conflict-serializable but is recoverable
C
S is both conflict-serializable and recoverable
D
S is neither conflict-serializable not is it recoverable
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