DSA presentation , E-R Model By TanveerSaleh

It is high-level data model, this model is used to define the data elements and relationship between for a specified system.

1. DATA base SYSTEM
PRESENTATION
Name:TanveerSaleh
Topic : E-R model
Visit: tanveersaleh.com

2. E-R model
introduction
oIt is high-level data model, this model is used to define the
data elements and relationship between for a specified
system.
oER Model is used to model the logical view of the system
from data perspective which consists of these components:

3. E-R model
Entity:
An Entity may be an object with a physical existence –a
particular person, car, house, or employee –or it may be an
object with a conceptual existence –a company, job, or a
university course.
Weak entity:
An entity on an other entity is called weak entity .

4. E-R MODEL
Attributes:
Attributes are theproperties which define the entity type.
For example.

5. E-R Model
Types of Attributes:
•Key Attribute.
•Composite Attribute.
•Multivalued Attribute.
•Derived Attribute.
Key Attribute:
The key attribute is use to represent main characteristics of
an
entity. In ER diagram, key attribute is represented by an
oval with
underlying lines.

6. E-R Model
Composite Attributes:
An attributecomposed of many other attributeis called as
composite
attribute. Composite attribute represented by ellipse. For
example,

7. oE-R Model
Multivalued Attribute:
An attribute consistingmore than one valuefor a given
entity.
In ER diagram, multivalued attribute is represented by
double oval.For
example.

8. E-R Model
Derived Attribute:
An attribute which can bederived from other attributesof
the entity type is known as derived attribute. e.g.; Age (can be
derived from DOB). In ER diagram, derived attribute is
represented by dashed oval.

9. E-R Model
The complete entity typeStudentwith its attributes can be
represented as:

10. E-R Model
Relations:
1.One to one relation
2.One to many relation
3.Many to one relation
4.Many to many relation

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