Database Homework Help

DATABASE HOMEWORK HELP

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Q1. Identify the correct statement(s) from the following. a) The overall physical structure of the database is called physical schema. b) The actual content of the database at a particular point in time is called an instance. c) Data dictionary does not contain any database schema. d) Physical schema describes how data is stored in the database and the relationships among the data Answer: a), b) Q2. Consider the following instance: MLDatabase Model

Accuracy

Dataset

Training Data

M1

98

GIVES

11280

M2

100

DB

29650

M2

NULL

DC

148

M2

100

GIVES

11280

M3

45

DC

148

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Identify the correct representation of MLDatabase schema. a) MLDatabase(Model, Accuracy, Dataset, Training Data) b) MLDatabase(Model, Accuracy, Dataset, Training Data) c) MLDatabase(Model, Accuracy, Dataset, Training Data) d) MLDatabase(Model, Accuracy, Dataset, Training Data) Answer: a) Q3. Identify the incorrect statement(s). a) A Super Key is a set of one or more attributes that, taken collectively, allows us to uniquely identify an entity in the entity set. b) A proper subset of a candidate key is called a Super Key. c) The minimal set of attributes that allows us to uniquely identify an entity in the entity set is called a candidate key. d) A proper subset of a Super Key is not always a Candidate Key. Answer: b) Q4. Consider two relations below. The primary keys are underlined.

Identify all possible foreign key(s) from the options. databasehomeworkhelp.com

Employee(EmpID, Ename, Salary) where EmpID is of type integer, Ename is of type string, and Salary is of type decimal number. Project(EmpID, Pnumber) where EmpID is of type integer, and Pnumber is of type string. a) Ename b) EmpID c) Pnumber d) EmpID, Pnumber Answer: b) Q5. Consider the following instance of ImageRec(SI, DepthImage, Coord1, Coord2).

SI

Depth Image

Coord1

Coord 2

1

256

1

1

2

256

1

2

3

194

6

6

8

126

6

6

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Which of the following is a Secondary Key in ImageRec? a) {SI, DepthImage} b) {Coord1, Coord2} c) (Coord2, DepthImage} d) {Coord1, DepthImage} Answer: c) Q6. Consider the following instances: Game 1

Game 1

Player

Score

P1 P1 P1 P2

20 50 80 90

Gamer

Attempt

P1 P2 P3

1 2 6

How many tuples will be selected by oPlayer = Gamer(Game1 x Game2)? a) 3 b) 4 c) 8 d) 9 databasehomeworkhelp.com

Answer: b) Q7. Consider the two tables given below: Student

Teacher

Roll

Name

Course

101

Sheema

French

112

Mala

English

213

Sita

French

Name

Course

FID

F

152

Sunita

Hindi

613

Abir

English

275

Darshik

French

F

Identify the correct statement from the following. a) Cartesian product of Student and Teacher has six tuples. b) Cartesian product of Student and Teacher is not possible. c) There will be three tuples in the result of the natural join between Student and Teacher. d) Natural join between Student and Teacher is not possible.

Answer: d) databasehomeworkhelp.com

Q8. Consider the following table:

a) b) c) d)

II (Branch=Address) A (Salary>10000) (Employee Details) II(Branch=Address) v (Salary>10000)(Employee Details) O(Branch=Address) A (Salary>10000) (EmployeeDetails) (Branch=Address) v (Salary>10000) (Employee Details)

Answer: c)

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Q9. Consider the following table:

a) R₁ R₂ b) R₂ R₁ c)( R₁ U R₂) n (R₁ R₂) d) (R₁ R₂) U (R₂ - R₁) Answer: c)

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Q10. Which of the following can be a candidate key for the following instance?

Employee Details Emp Name

Branch

Address

Salary

Raja

Kolkata

Kolkata

10000

Priyanka

Mumbai

Hyderabad

12000

Raja

Bangalore

Kolkata

10000

Rumki

Hyderabad

Hyderabad

20000

Sumit

Hyderabad

Bangalore

10000

Sandip

Mumbai

Mumbai

15000

a) {EmpName} b) {Branch} c) {EmpName, Address} d) {EmpName, Branch} Answer: d) databasehomeworkhelp.com