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

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