Databases Test 1

Question 1
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Consider the following set of functional dependencies F on the schema S(P, Q, R)
F = {P → QR, PQ → R, Q → R, P → Q}
The canonical cover of the above given set is

A
P → QR and PQ → R

B
P → QR and P → Q

C
P → Q and Q → R

D
P → QR and Q → R

Question 2
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Which of the following concurrency control protocol ensures both conflict serializability and free from deadlock?

A
Time stamp ordering

B
2 Phase locking

C
Both (a) and (b)

D
None of the above

Question 3
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Let the two-relation schema be R (A, B,) and S (A, B). which of the following is not equivalent to R ∩ S

A
R – (R – S)

B
S – (S - R)

C
R U S – ((S – R) – (R – S))

D
((R U S – (S – R)) – (R – S)

Question 4
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Consider a relation R(X, Y, Z, W) where X, Y, and Z are attributes and the functional dependencies are X → Y and X → Z.
What is the number of functional dependencies possible with attribute X?

A
8-8

B
84-81

C
87-86

D
89-82

Question 5
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The following table has two attributes X and Y where X is the primary key and Y is the foreign key referencing X with on-delete cascade.
X
Y
2
4
3
4
4
3
5
2
7
2
9
5
6
4

The set of all tuples that must be additionally deleted to preserve referential integrity when the tuple (3, 4) is deleted is:

A
(4, 3), (2, 4) and (6, 4)

B
(4, 3), (2,4), (6, 4), (5, 2) and (7, 2)

C
(3, 4), 4, 3), (2,4), (6, 4), (5, 2), (7, 2) and (9, 5)

D
(4, 3), (2,4), (6, 4), (5, 2), (7, 2) and (9, 5)

Question 6
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Given two table R1 (x, y) and R2(y, z) with 50 and 30 number of tuples respectively. Find maximum number of tuples in the output of natural join between tables R1 and R2 i.e. R1 * R2? (* - Natural Join)

A
30

B
20

C
50

D
1500

Question 7
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Consider a B+ tree in which the minimum number of keys in a node is 23. What is the maximum number of keys in any non-root node?

A
47-47

B
474-471

C
477-476

D
479-472

Question 8
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Assume that there are two transactions T1 and T2 of which T1 started execution before T2. Consider the following schedule involving two transactions T1 and T2
T1:r(A) T2: r(B) T2:w(A) T1:w(A)
Which of the following is true about the following schedule

A
It is allowed under basic timestamp order protocol but not under Thomas write rule

B
It is not allowed under basic timestamp order protocol but allowed under Thomas write rule

C
It is allowed under basic timestamp order protocol as well as Thomas write rule

D
It is not allowed under both basic timestamp order protocol and Thomas write rule

Question 9
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Given below is an instance of the MENTOR relation:
MentorID
Name
Salary
Age
Department
1001
Priya
10000
23
English
1002
Sheenam
20000
25
Maths
1003
Priya
25000
X
Maths
1004
Renu
10000
25
Science
1005
Renu
12000
27
English

For (Name, Age) to be a key for this instance, the value X should not be equal to_________.

A
23

B
25

C
27

D
Any value

Question 10
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If R(ABC) with FDs = AB → C, AC → B, BC → A, then what is the strongest normal form that is not violated by this relation?

A
2NF

B
3NF

C
BCNF

D
1NF

Question 11
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Consider the following query :
SELECT E.eno, COUNT(*)
FROM Employees E
GROUP BY E.eno
If an index on eno is available, the query can be answered by scanning only the index if

A
the index is only hash and clustered

B
the index is only B+ tree and clustered

C
index can be hash or B+ tree and clustered or non-clustered

D
index can be hash or B+ tree and clustered

Question 12
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Consider the relation R = {ABCDEG} and set of FDs are F = {AB → C, AC → B, AD → E, B →D, BC → A, E → G}, then the decomposition {ABC, ACDE, ADG} is

A
lossless but not dependency preserving

B
dependency preserving but not lossless and

C
lossless and dependency preserving

D
Neither lossless and nor dependency preserving

Question 13
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Consider a relation book (title, price) which contains the titles and prices of different books.
Assuming that no two books have the same price, what does the following SQL query list ?
Select title
from book as B
where (select count (*)
from book as T
where T.price > B.price) < 7

A
Titles of the six most expensive books

B
Title of the sixth most expensive books

C
Titles of the seven most expensive books

D
Title of the seventh most expensive books

Question 14
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In a relational schema R(P, Q, R, S, T, V) with functional dependencies are given below:
P → RS
R → SV
S → Q
T → P
What is the number of superkey possible in R?

A
32-32

B
324-321

C
327-326

D
329-322

Question 15
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Consider the following relation schema R and S along with their tuple sets.
R(A, B) = {<a1, b1 >, <a2, b1>, <a3, b1>, <a4, b1), <a1, b2>, <a3, b2>, <a2, b3>, <a3, b3>, <a4, b3>, <a1, b4>, <a2, b4>, <a3, b4>}
S(A) = {a1, a2, a3}
What is the value of T ← R/S, where “/” represents the Relational Algebra “division” operation?

A
T(B) = {b1, b2, b4}

B
T(B) = {b1, b3, b4}

C
T(B) = {b1, b4)

D
T(B) = {b1, b3}

Question 16
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Consider the following tuple relational calculus:
{t | Ǝ s ε instructor (t[name] = s[name]
ᴧ Ǝ u ε department (u[dept_name] = s[dept_name]
ᴧ u[building] = “Taylor”))}
What does the given expression perform?

A
Finds the names of departments in the Taylor building.

B
Finds the names of all instructors whose department is in the Taylor building.

C
Finds the names of instructors who do not work in the Taylor building.

D
Finds the names of all instructors whose department name is Taylor.

Question 17
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Database table name Group_A and Group_B is given below
Group_A
Roll_no
Student_Name
Age
10
X
18
15
Z
20
19
Y
17
22
Z
19
89
Y
21
22
Y
20

Group_B
Roll_no
Student_Name
Age
06
X
19
25
V
21
19
Y
18
2
Z
20
22
W
17

How many tuples does the result of the following SQL query contain?
Select Group_A.Roll_no
FROM Group_A
Where Group_A.age > All(SELECT Group_B.Age
FROM Group_B
where Group_B.Student_Name = ‘Y’)

A
4-4

B
44-41

C
47-46

D
49-42

Question 18
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Relation R has eight attributes ABCDEFGH. Fields of R contain only atomic values.
F={CH→G, A→BC, B→CFH, E→A, F→EG} is a set of functional dependencies (FDs) so that F⁺ is
exactly the set of FDs that hold for R.
The relation R is

A
in 1NF, but not in 2NF

B
in 2NF, but not in 3NF

C
in 3NF, but not in BCNF.

D
in BCNF.

Submit Test

MentorID	Name	Salary	Age	Department
1001	Priya	10000	23	English
1002	Sheenam	20000	25	Maths
1003	Priya	25000	X	Maths
1004	Renu	10000	25	Science
1005	Renu	12000	27	English

Group_A
Roll_no	Student_Name	Age
10	X	18
15	Z	20
19	Y	17
22	Z	19
89	Y	21
22	Y	20

Group_B
Roll_no	Student_Name	Age
06	X	19
25	V	21
19	Y	18
2	Z	20
22	W	17

Databases Test ...

Question 1

P → QR and PQ → R

P → QR and P → Q

P → Q and Q → R

P → QR and Q → R

Question 2

Time stamp ordering

2 Phase locking

Both (a) and (b)

None of the above

Question 3

R – (R – S)

S – (S - R)

R U S – ((S – R) – (R – S))

((R U S – (S – R)) – (R – S)

Question 4

8-8

84-81

87-86

89-82

Question 5

(4, 3), (2, 4) and (6, 4)

(4, 3), (2,4), (6, 4), (5, 2) and (7, 2)

(3, 4), 4, 3), (2,4), (6, 4), (5, 2), (7, 2) and (9, 5)

(4, 3), (2,4), (6, 4), (5, 2), (7, 2) and (9, 5)

Question 6

30

20

50

1500

Question 7

47-47

474-471

477-476

479-472

Question 8

It is allowed under basic timestamp order protocol but not under Thomas write rule

It is not allowed under basic timestamp order protocol but allowed under Thomas write rule

It is allowed under basic timestamp order protocol as well as Thomas write rule

It is not allowed under both basic timestamp order protocol and Thomas write rule

Question 9

23

25

27

Any value

Question 10

2NF

3NF

BCNF

1NF

Question 11

the index is only hash and clustered

the index is only B+ tree and clustered

index can be hash or B+ tree and clustered or non-clustered

index can be hash or B+ tree and clustered

Question 12

lossless but not dependency preserving

dependency preserving but not lossless and

lossless and dependency preserving

Neither lossless and nor dependency preserving

Question 13

Titles of the six most expensive books

Title of the sixth most expensive books

Titles of the seven most expensive books

Title of the seventh most expensive books

Question 14

32-32

324-321

327-326

329-322

Question 15

T(B) = {b1, b2, b4}

T(B) = {b1, b3, b4}

T(B) = {b1, b4)

T(B) = {b1, b3}

Question 16

Finds the names of departments in the Taylor building.

Finds the names of all instructors whose department is in the Taylor building.

Finds the names of instructors who do not work in the Taylor building.