Entity relationship(er) model

Entity Relationship Model
Rahul Khanvani
BinaryBuzz.Wordpress.com
Presentation on:
Rahul Khanvani For More Visit BinaryBuzz.Wordpress.com

• The approach of
concentrating on database
structures constraints
during database design we
present the model concept of
Entity Relationship (ER)
Model.

• Frequently used in
conceptual design of
database applications.
• Diagrammatic notation
associated with ER model
is called ER diagrams

1) Requirement
collection &
analysis
1) Data
Requirements.
2) Functional
Requirements.
3) User Defined
Operations-
Transections.Rahul Khanvani For More Visit BinaryBuzz.Wordpress.com

1) Conceptual
Schema/Design
1) Include Implementation
details.
2) Implementation Of
Database
1) Logical Design.
3) Physical Design
1) Internal Storage
Structure.Rahul Khanvani For More Visit BinaryBuzz.Wordpress.com

• Entities:
▫ Entities Specifies
Individual Items in
an Application
 Person
 Picture
 Thing
 Concept
 Process

•Relationship:
▫A relationship is
defined as an
association
among Entities.

•Attributes:
▫ Each Entity has
specific characteristic
that is defined by
attribute.
Student Entity has
Name
Address
Result as attributes.

• The basic object to the ER
Model
• Which is a thing in real
world
• It may be an Object With
▫ Physical Existence
 Person , Car , House ,
Employee.
▫ Conceptual Existence
 Company , Job , Course.Rahul Khanvani For More Visit BinaryBuzz.Wordpress.com

E-R Diagram
Relationship
Entity
Attributes
• Every Entity has an
Attribute- particular
Property
To describe It.
• For Example
EMPLOYEE Entity
Described by
Employee’s
▫ Name ,Address
▫ Salary,JobRahul Khanvani For More Visit BinaryBuzz.Wordpress.com

1. Composite & Single
Attributes
2. Single valued &
Multi valued
Attributes
3. Stored & Derived
Attributes
4. Null valued
Attributes &
Complex AttributesRahul Khanvani For More Visit BinaryBuzz.Wordpress.com

Composite & Simple Attribute
• Composite Attribute Are Those which can
be divided into smaller subparts which
represent more attributes with independent
meaning.
▫ Employee address divided into street address
,city , state & zip(pin).
• Attributes that are not divisible
are called simple Attributes.
Composite & Simple Attribute

Address
Street
Add
Street no
Apartment
name
Apartment
no
city pin state

Single Valued & Multi valued
Attributes
•An Attribute has a
single value for
particular entity is
called single valued
Attribute
▫ Phone no Of employee
▫ Age of employee.

• If an Attribute can have set of values
for the same entity is known as Multi-
valued Attribute.
• For Example
▫ College Degree
▫ One person may not have degree,
another may have one , A third person
may have two.
▫ So at that time Attribute Should be
Multi-Valued.

Degree
S.S.C
H.S.C
F.Y
S.Y
T.YRahul Khanvani For More Visit BinaryBuzz.Wordpress.com

Stored & Derived Attribute
• An attribute which is
derivable from another
Attribute is called derived
attribute.
▫ Age is derived from Birth date.
• Where the derived attributes
derivable from the base
attribute so the base attribute
is stored attribute.
Stored & Derived Attribute

Current
Date
Birth
date
Age
Stored
Attribute
Derived
Attribute

• When a particular entity set have any applicable
value for an attribute so it considered as null
value attribute.
▫ Fax No.
▫ Tele. No.
• Complex Attribute
▫ Complex attributes are nothing but combination
of composite and multi value attributes.
Null Value & Complex Attribute

• {Phone(areacode,P
honeno)}
Address_
phone
• (Number ,
• street,
• apartment_number)
city , state
,zip))
Address(
Street
Address

Entity types & entity Sets
• An entity type defines a collection or set of
entities that have same attributes.
• Entity types that do not have key attributes of
their own are called weak entity.

Name
Ram
Om
Age
25
37
Salary
20000
30000
Entity Type
Entity
Set

• An important constraint on entity of
an entity type in the key or
uniqueness constraint.
• Hose values are distinct for each
individual entity in entity set.
• Used to identify each entity Uniquely
Called Key Attribute.
▫ For Example
 Employee Number
Key attributes

Value Sets(Domains)
of attributes
• Each Simple attribute of an entity type is
associated with the value set which
specifies set of values Assigned to the
Attributes.
▫ Employee salary-Numeric Value Set
▫ Employee Name-String/Char Value Set
• Value set are not displayed in E-R
Diagram
• Specified as Basic data-type Available in
most programming language.Rahul Khanvani For More Visit BinaryBuzz.Wordpress.com

• Whenever an attribute one entity type
refers to another entity type Is
indicates the relation between one
entity to another.

• One To One(1:1) :
• One To Many(1:M) :
• Many To Many(M:N)
Relationship Types

• The One To One relationship between entity set
indicates that for each entity there in one most
entity associated with it.
▫ For example
▫ One department has only one Manager.
One To One Relationship
Manager DepartmentHas
11

• The One To Many relationship between entity
set indicates that for each entity there is no of
entities associated with it.
▫ For example
▫ One employee has No Of employees.
One To Many Relationship
Manager EmployeeHas
M1

• The Many To Many relationship between entity
set indicates that There is no restrictions Entities
have no of entity sets associated with it.
▫ For example
▫ One employee has No Of employees.
Many To Many Relationship
Employee ProjectHas
NM

Thank You
Prepared By…
Rahul Khanwani..

Entity relationship(er) model

More Related Content

What's hot (10)

Viewers also liked (15)

Similar to Entity relationship(er) model (20)

More from Rahul Khanwani (7)

Recently uploaded (20)

Entity relationship(er) model