Databases Test 2

Question 1
2 / -0.33

A relation R(A, B, C) having the following tuples (2, 3, 4) (4, 1, 2) (5, 2, 2) (1, 3, 2). Which of the following functional dependency does not hold true from this relation?

A
B -> C

B
A -> B

C
AC -> B

D
BC -> A

Question 2
2 / -0.33

Which of the following is/are not a part of the ACID properties of database transactions?

A
Atomicity

B
Consistency

C
Duration

D
Independent

Question 3
2 / -0.33

Consider the following relational schema for students(STU):
id
name
age
marks
1
PPP
13
56
2
QQQ
14
67
3
RRR
13
76
4
AAA
15
56
5
BBB
14
58
6
CCC
16
79
7
SSS
16
80
8
TTT
13
73
9
RRR
14
54
10
YYY
15
42
The following query is made on the database.
T1 → \({{\rm{\Pi }}_{id,name}}\left( {{\sigma _{age > 13 \wedge age < 16}}\left( {STU} \right)} \right)\)
T2 → \({{\rm{\Pi }}_{id,name}}\left( {{\sigma _{marks > 55 \wedge marks < 66}}\left( {STU} \right)} \right)\)
T → T2 - T1
The total no. of rows in T is ______.

A
1-1

B
14-11

C
17-16

D
19-12

Question 4
2 / -0.33

Let Account be a relation with attributes (customer_name, amount). Consider
(i) {T |~Tϵ Account}
(ii) {T | T ϵ Account}
Which of the following statement is correct about this?

A
Only (i) is safe expression

B
Only (i) is unsafe expression

C
Only (ii) is unsafe expression

D
(i) and (ii) both are safe expressions

Question 5
2 / -0.33

Records are stored in some sorted order based on some search key and that search key is also sorted, is

A
Primary Indexing

B
Clustered Indexing

C
Secondary Indexing with key

D
Secondary Indexing with non-key

Question 6
2 / -0.33

Let X (a, b, c, d) and Y (p, q, r, s) be two relations in which a is the foreign key of X that refers to the primary key of Y. Which of the following operation does not causes the referential integrity constraint violation?

A
Delete from Y

B
Insert into Y

C
Delete from X

D
Insert into X

Question 7
2 / -0.33

Consider 4 transactions T1, T2, T3, and T4 Transaction T1 has 5 transactions, T2 has 4 transactions, T3 has 3 transactions and T4 has 2 transactions. What is the number of non-serial schedule?

A
2522496-2522496

B
25224964-25224961

C
25224967-25224966

D
25224969-25224962

Question 8
2 / -0.33

Which of the following statement is/are true?
I. A transaction writes a data item after it is read by an uncommitted transaction leads to an irrecoverable error in a database system.
II. Timestamp ordering protocol does not ensure freedom from deadlock
III. In case of disk crash, Among the ACID property, the durability property fails to make changes successfully in the database

A
Only I

B
Only II and III

C
I and III

D
None of these

Question 9
2 / -0.33

Consider a schema R(X, Y, Z W) and functional dependencies X → Y and W → Z. Then the decomposition of R into T1(X, Y) and T2(Z, W) is

A
Dependency preserving and lossless join

B
Dependency preserving but not lossless join

C
Not dependency preserving but lossless join

D
Neither dependency preserving nor lossless join

Question 10
2 / -0.33

Which of the following is/are true if a relation R has six attributes A, B, C, D, E, and F. The following functional dependencies hold AB → C, B → D, AD → F, C → D, D → E, E → F, F → D.

A
The number of super keys of R₁(DEF) is 7

B
In R1(DEF), Only D and E are candidate key

C
In R1(DEF), Only D and F are candidate key

D
In R₁(DEF), D, E, and F are candidate key

Question 11
2 / -0.33

Which of the following is true for the below given functional dependencies of the relation R(X, Y,Z,W) and S(X, Y, Z, W)?
R: {X → Y, XY → Z, W → XZ, Z → W}
S: {X → YZ, W → XY}
I. R ⊇ S
II. S ⊇ R

A
Only I

B
Only II

C
Both I and II

D
None of these

Question 12
2 / -0.33

Consider a relation R(ABC) with Functional dependency {AB → C, AC → B, BC → A}.Which of the following is/are TRUE about the normal form that the relation R is in?

A
2NF

B
3NF

C
BCNF

D
1NF

Question 13
2 / -0.33

Database table name Tuition_Records is given below
Students
Teachers
Fees
Aniket
Uday
10000
Barbie
Rishi
7000
Chandresh
Uday
12000
Dharma
Rishi
9000

SELECT count(*) FROM ((SELECT students, Teachers FROM Tuition_Records) AS A NATURAL JOIN (SELECT Teachers, Fees FROM Tuition_Records))
What is the output of the following SQL query?

A
8-8

B
84-81

C
87-86

D
89-82

Question 14
2 / -0.33

Consider the schema
Sailors(sid, sname, rating, age) with the following data
Sid
Sname
Rating
age
22
Dustin
7
45
29
Borg
1
33
31
Pathy
8
55
32
Robert
8
25
58
Raghu
10
17
64
Herald
7
35
71
Vishnu
10
16
74
King
9
35
85
Archer
3
26
84
Bob
3
64
96
Flinch
3
17
For the query
SELECT S.rating, AVG(S.age) AS avgage FROM Sailors S
Where S.age >= 18
GROUP BY S.rating
HAVING 1 < (SELECT COUNT(*) FROM Sailors S2 where S.rating = S2.rating)
The number of rows returned is

A
6

B
5

C
4

D
3

Question 15
2 / -0.33

Consider the following schedule of transactions T1, T2, T3 and T4.
T2: R(Y) T2: R(X); T3: R(X); T3: commit; T1:W(X); T2:W(Y); T2: R(z); T2: commit; T4: R(X); T4: R(Y); T1:W(Z); T1:commit; T4:commit.
Which of the following is correct about this?

A
S is conflict serializable

B
S is recoverable

C
S is cascadeless

D
None of these

Question 16
2 / -0.33

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.
How many candidate keys does the relation R have?

A
3

B
4

C
5

D
6

Question 17
2 / -0.33

Consider a file based system in which total overhead for each entry in the file allocation table is 2 bytes in size. Given a 100 × 10⁴ bytes of disk on which file system is stored. Block size of data is 10² bytes, then the maximum file size possible that can be stored on the disk is(in 10⁴ bytes)?

A
98

B
99

C
95

D
97

Question 18
2 / -0.33

Consider the database that has the relation schema T (X, Y). An instance of the schema T is as given below:
T1 ← ∏_Y (σ _{X = A3}(T))
T2 ← T ÷ T1
X
Y
A1
B1
A1
B2
A2
B1
A2
B2
A1
B3
A3
B1
A3
B2
A2
B1
A4
B1
A3
B3
A4
B2

Find the number of rows in T2

A
2-2

B
24-21

C
27-26

D
29-22

Question 19
2 / -0.33

Which of the following is/are true?

A
All M:N relationships should be converted into separate tables.

B
All 1:M and 1:1 relationship should be converted into separate tables.

C
All multi-valued attributes should be converted into separate tables.

D
Cardinality ratio is applicable for only binary relationships.

Question 20
2 / -0.33

Consider the following transactions with data items X and Y initialized to zero:
T₁: read (x);
Read (y);
if x = 0 then y: = y + 1;
Write (y);
T₂: read (y);
write (x);
If y = 0 then x: x + 1
Write (x);
The concurrent execution of T₁ and T₂ lead to

A
Serializable schedule

B
A schedule that is not conflict serializable

C
A conflict serializable schedule

D
A schedule for which a precedence graph cannot be drawn

Submit Test

id	name	age	marks
1	PPP	13	56
2	QQQ	14	67
3	RRR	13	76
4	AAA	15	56
5	BBB	14	58
6	CCC	16	79
7	SSS	16	80
8	TTT	13	73
9	RRR	14	54
10	YYY	15	42

Students	Teachers	Fees
Aniket	Uday	10000
Barbie	Rishi	7000
Chandresh	Uday	12000
Dharma	Rishi	9000

Sid	Sname	Rating	age
22	Dustin	7	45
29	Borg	1	33
31	Pathy	8	55
32	Robert	8	25
58	Raghu	10	17
64	Herald	7	35
71	Vishnu	10	16
74	King	9	35
85	Archer	3	26
84	Bob	3	64
96	Flinch	3	17

Databases Test ...

Question 1

B -> C

A -> B

AC -> B

BC -> A

Question 2

Atomicity

Consistency

Duration

Independent

Question 3

1-1

14-11

17-16

19-12

Question 4

Only (i) is safe expression

Only (i) is unsafe expression

Only (ii) is unsafe expression

(i) and (ii) both are safe expressions

Question 5

Primary Indexing

Clustered Indexing

Secondary Indexing with key

Secondary Indexing with non-key

Question 6

​Delete from Y

Insert into Y

Delete from X

Insert into X

Question 7

2522496-2522496

25224964-25224961

25224967-25224966

25224969-25224962

Question 8

Only I

Only II and III

I and III

None of these

Question 9

Dependency preserving and lossless join

Dependency preserving but not lossless join

Not dependency preserving but lossless join

Neither dependency preserving nor lossless join

Question 10

The number of super keys of R1(DEF) is 7

In R1(DEF), Only D and E are candidate key

In R1(DEF), Only D and F are candidate key

In R1(DEF), D, E, and F are candidate key

Question 11

Only I

Only II

Both I and II

None of these

Question 12

2NF

3NF

BCNF

1NF

Question 13

8-8

84-81

87-86

89-82

Question 14

6

5

4

3

Question 15

S is conflict serializable

S is recoverable

S is cascadeless

None of these

Question 16

3

4

5

Delete from Y

The number of super keys of R₁(DEF) is 7

In R₁(DEF), D, E, and F are candidate key