Advanced Database Management System - Tutorials and Notes: Entity Relationship Model (ER model) Quiz Questions with solutions

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Thursday, 13 August 2020

Entity Relationship Model (ER model) Quiz Questions with solutions

 ER model solved quiz, Entity relationship model into conceptual schema solved quiz, ERD solved exercises

Entity Relationship Model - Quiz Questions

  Use this ER diagram to answer the questions below;


Entity Relationship Diagram

1. While reducing the above ER diagram into schema, we will get only two conceptual schemas namely, Pilot and Plane.

(a) TRUE                                 (b) FALSE

Answer:

Option (b)

We will get three. The relationship will also be converted into separate schema as it is a many-to-many relationship.

 

2. Which of the following is correct about reduction of the given ER diagram into schema?

(a) Pilot(PID, PName, Hours_Flying, Address, Phone), Plane(Plane_ID, Operator, Source, Destination, Model), flies(PID, Plane_ID)

(b) Pilot(PID, PName, Hours_Flying, Address, Phone), Plane(Plane_ID, Operator, Source, Destination, Model), flies(PID, Plane_ID)

(c) Pilot(PID, PName, Hours_Flying, Address, Phone), Plane(Plane_ID, Operator, Source, Destination, Model, PID)

(d) Pilot(PID, PName, Hours_Flying, Address, Phone, Plane_ID), Plane(Plane_ID, Operator, Source, Destination, Model)

Answer:

Option (b).

Though option (a) looks very similar to option (b), the keys are missing in (a).

 

3. Which of the following statement(s) is/are true about the given ER diagram?

(a) A pilot flies zero or more planes

(b) Each pilot flies only one plane

(c) A plane is operated by only one pilot

(d) A plane is operated by zero or more pilots

Answer:

Options (a) and (d)

‘flies’ is a many-to-many relationship. As per the ERD, a pilot entity is related to zero or more plane entities. And, a plane entity is related to zero or more pilot entities. Hence, both options (a) and (d) are correct.

 

4. Inclusion of PID in the schema of Plane or Plane_ID in the schema of Pilot results in __________

(a) No redundancy

(b) Minimal redundancy

(c) Data redundancy

(d) None of the above

Answer:

Option (c)

If we include PID in the schema of plane, then for each plane operated by the particular pilot, the pilot id will be repeated. Also, if the plane is operated by more than one pilot, the Plane_ID, Operator, Source, Destination, and Model attribute values are repeated.

Example:

Why don’t we include the primary key of participating entity sets into one another in case if the relationship is many-to-many?

Pilot:

PID

PName

Hours_Flying

Address

Phone

P101

Kumar

1300

Chennai

0078675645

P102

Martin

200

Vellore

9011110000

Plane:

Plane_ID

Operator

Source

Destination

Model

PL_1

Jet

Chennai

New Delhi

X123

PL_3

Air India

Bengaluru

Chennai

AS10

If suppose, pilots P101 and P102 have operated plane PL_1 during some flights, then inclusion of PID into Plane will result in redundancy as follows;

Plane with PID as foreign key:

Plane_ID

Operator

Source

Destination

Model

PID

PL_1

Jet

Chennai

New Delhi

X123

P101

PL_1

Jet

Chennai

New Delhi

X123

P102

PL_3

Air India

Bengaluru

Chennai

AS10

P102

 

5. Which of among the following are true if we create a separate table for the relationship ‘flies’?

(a) PID and Plane_ID are foreign keys referencing the relations Pilot and Plane respectively

(b) PID and Plane_ID together forms the key for ‘flies’

(c) PID is the only key of ‘flies’

(d) Plane_ID is the only key of ‘flies’

Answer:

Options (a) and (b)

While we create separate table for many-to-many relationship, we include the keys of participating entity sets into the new table as foreign keys and also, all the attributes (except descriptive attribute, if any) will together form the key for the new table.

 

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