GATE CSE topic:databases PYQs & Answers — Page 6

Questions 51–60 of 73. Imported answers require independent review unless marked reviewed.

Which one of the following is used to represent the supporting many-one relationships of a weak entity set in an entity-relationship diagram?

Your answerChoose one option.

Diamonds with double/bold border

Rectangles with double/bold border

Ovals with double/bold border

Ovals that contain underlined identifiers

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Consider a relational table

that is in 3NF, but not in BCNF. Which one of the following statements is TRUE?

Your answerChoose one option.

has a nontrivial functional dependency

, where

is not a superkey and

is a prime attribute.

has a nontrivial functional dependency

, where

is not a superkey and

is a non-prime attribute and

is not a proper subset of any key.

has a nontrivial functional dependency

, where

is not a superkey and

is a non-prime attribute and

is a proper subset of some key.

A cell in

holds a set instead of an atomic value.

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Consider a schedule of transactions

and

Diagram for Computer Science and Information Technology question 37

Here, RX stands for “Read(X)” and WX stands for “Write(X)”. Which one of the following schedules is conflict equivalent to the above schedule?

Your answerChoose one option.

Diagram for Computer Science and Information Technology question 37 (figure 2)

Diagram for Computer Science and Information Technology question 37 (figure 3)

Diagram for Computer Science and Information Technology question 37 (figure 4)

Diagram for Computer Science and Information Technology question 37 (figure 5)

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Consider a database implemented using B+ tree for file indexing and installed on a disk drive with block size of 4 KB. The size of search key is 12 bytes and the size of tree/disk pointer is 8 bytes. Assume that the database has one million records. Also assume that no node of the B+ tree and no records are present initially in main memory. Consider that each record fits into one disk block. The minimum number of disk accesses required to retrieve any record in the database is ______.

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Consider the following two statements about database transaction schedules:

I. Strict two-phase locking protocol generates conflict serializable schedules that are also recoverable.

II. Timestamp-ordering concurrency control protocol with Thomas’ Write Rule can generate view serializable schedules that are not conflict serializable.

Which of the above statements is/are TRUE?

Your answerChoose one option.

I only

II only

Both I and II

Neither I nor II

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Which one of the following statements is NOT correct about the B+ tree data structure used for creating an index of a relational database table?

Your answerChoose one option.

B+ Tree is a height-balanced tree

Non-leaf nodes have pointers to data records

Key values in each node are kept in sorted order

Each leaf node has a pointer to the next leaf node

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Let the set of functional dependencies

hold on a relation schema

is not in BCNF. Suppose

is decomposed into two schemas

and

, where

and

. Consider the two statements given below. I. Both

and

are in BCNF II. Decomposition of

into

and

is dependency preserving and lossless Which of the above statements is/are correct?

Your answerChoose one option.

Both I and II

I only

II only

Neither I nor II

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A relational database contains two tables Student and Performance as shown below:

Student

Roll no.	Student name
1	Amit
2	Priya
3	Vinit
4	Rohan
5	Sita

Performance

Roll no.	Subject_code	Marks
1	A	86
1	B	95
1	C	90
2	A	89
2	C	92
3	C	80

The primary key of the Student table is Roll_no. For the Performance table, the columns Roll_no. and Subject_code together form the primary key. Consider the SQL query given below:

SELECT S.Student_name, sum(P.Marks) FROM Student S, Performance P WHERE P.Marks > 84 GROUP BY S.Student_name;

The number of rows returned by the above SQL query is ________.

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Consider the following relations P(X,Y,Z), Q(X,Y,T) and R(Y,V).

X	Y	Z
X1	Y1	Z1
X1	Y1	Z2
X2	Y2	Z2
X2	Y4	Z4

X	Y	T
X2	Y1	2
X1	Y2	5
X1	Y1	6
X3	Y3	1

Y	V
Y1	V1
Y3	V2
Y2	V3
Y2	V2

How many tuples will be returned by the following relational algebra query?

Answer: ________.

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In an Entity-Relationship (ER) model, suppose R is a many-to-one relation from entity set E1 to entity set E2. Assume that E1 and E2 participate totally in R and that the cardinality of E1 is greater than the cardinality of E2.

Which one of the following is true about R?

Your answerChoose one option.

Every entity in E1 is associated with exactly one entity in E2.

Some entity in E1 is associated with more than one entity in E2.

Every entity in E2 is associated with exactly one entity in E1.

Every entity in E2 is associated with at most one entity in E1.

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GATE CSE topic:databases PYQs

Question 14

Question 36

Question 37

Question 54

Question 11

Question 14

Question 32

Question 51

Question 55

Question 11