Lecture 4- Entity Relations Model

Question 1

Describe the database design process

Answer 1

Question 2

What are the three things that describe ER model

Answer 2

1. Entities
2. Relationships
3. Attributes

Question 3

What is an entity?

Answer 3

A distinguishable object

Question 4

What is an entity set?

Answer 4

A set of entities fo the same type

Question 5

What is a relationship?

Answer 5

Represents the fact that certain entities are related to each other

Question 6

What is a relationship set?

Answer 6

Set of relationships of the same type

Question 7

What is an attribute?

Answer 7

Describes a property of an entity or a relationship

Question 8

What is a key?

Answer 8

A minimal set of attributes that uniquely identifies each entity in an entity set

Question 9

What is a role?

Answer 9

The function of an entity set in a relationship set

Question 10

What type of relationship is this?

Answer 10

Binary, many to many

Question 11

What type of relationship is this?

Answer 11

Binary, many to one

Question 12

What type of relationship is this?

Answer 12

Binary, one to one

Question 13

What type of relationship is this?

Answer 13

Ternary relationship

Question 14

What type of relationship is this?

Answer 14

Participation constraint

Question 15

What is this double circle?

Answer 15

Set value attributes

Question 16

What relationship is this?

Answer 16

Weak entity

Question 17

What is a weak entity?

Answer 17

A weak entity models an entity which is part of an owner entity, and it cannot be uniquely identified without the primary key of the owner entity

Question 18

What type of relationship is a weak entity?

Answer 18

Many to one

Question 19

____ cannot be uniquely identified by their own attributes alone and rely on the strong entitys primary key for their identification

Answer 19

Weak entities

Question 20

What type of relationship is this?

Answer 20

ISA Hierarchy

Question 21

What are some properties of ISA?

Answer 21

• Inheritance
• Transitivity = hierarchy of IsA
• Reasons for using IsA

Question 22

Superclass vs subclass

Answer 22

• Superclass = generalization (it contains attributes that are common to all entities in the hierarchy)
• Subclass = specialization (it inherits all the attributes of the superclass and can have additional attributes of its own)

Question 23

Review the types of relationships

Answer 23

Question 24

Create this table

Answer 24

Question 25

Create this table

Answer 25

Question 26

Create this table

Answer 26

Question 27

Create this table

Answer 27

Relationship with constraints

Question 28

Create this table

Answer 28

Relationship with constraints

Question 29

Create this table

Answer 29

Participation constraints

Question 30

Create this table

Answer 30

Weak entities

Question 31

Create this table

Answer 31

Set value attributes

Question 32

Create this table

Answer 32

IsA Hierarchy