Enhanced ER-model in tamil | unit -2 cse sem -4 | epi-2.3 |

topic covered in this video :-
Enhanced ER-model unit -2 DATABASE DESIGN for computer science engineering in 4th sem
playlist of dbms subject :-
• Database Management sy...
join to our telegram channel to download the pdf used in this video:
t.me/cseengine...
DATABASE MANAGEMENT SYSTEMS
unit-2
Enhanced ER-model
2
Course Outline:-
UNIT II DATABASE DESIGN
- Enhanced-ER Model
THE ENHANCED ER MODEL
As the complexity of data increased in the late 1980s, it be came more and more difficult to use
the traditional ER Model for database modelling. Hence some improvements or enhancements
were made to the existing ER Model to make it able to handle the complex applications better.
EER is a high-level data model that incorporates the extensions to the original ER model.
It is a diagrammatic technique for displaying the following concepts
Sub Class and Super Class
Specialization and Generalization
Union or Category
Aggregation
These concepts are used when the comes inEER schema and the resulting schema diagrams
called as EER diagrams.
4
Features of EER Model
EER creates a design more accurate to database schemas.
It reflects the data properties and constraints more precisely.
It includes all modelling concepts of the ER model.
Diagrammatic technique helps for displaying the EERschema.
It includes the concept of specialization and generalization.
It is used to represent a collection of objects that is union of objects of different of
different entity types.
5
A. Sub Class and Super Class
Sub class and Super class relationship leads the concept of Inheritance. The relationship
between sub class and super class is denoted with symbol.
1. Super Class:
Super class is an entity type that has a relationship with one or more subtypes. An entity cannot exist in database
merely by being member of any super class.
For example: Shape super class is having sub groups as Square, Circle, Triangle.
2. Sub Class:
Sub class is a group of entities with unique attributes.
Sub class inherits properties and attributes from its super class.
6
Enhanced ER Model
Hence, as part of the Enhanced ER Model, along with other improvements, three new
concepts were added to the existing ER Model, they were:
1. Generalization
2. Specialization
3. Aggregation
7
1. Generalization
Generalization is a bottom-up approach in which two lower level entities combine to form a
higher level entity . In generalization, the higher level entity can also combine with other
lower level entities to make further higher level entity.
It's more like Superclass and Subclass system, but the only difference is the approach, which
is bottom-up. Hence, entities are combined to form a more generalised entity, in other words,
sub-classes are combined to form a super-class.
For example, Saving and Current account types entities can be
generalised and an entity with name Account can be created,
which covers both.
8
Generalization example
9
2. Specialization
-Specialization is a process that defines a group entities which is divided into sub
groups based on their characteristic.
-It is a top down approach, in which one higher entity can be broken down into two
lower level entity.
-It maximizes the difference between the members of an entity
by identifying the unique characteristic or attributes of each member.
-It defines one or more sub class for the super class and also forms
the superclass subclass relationship.
10
3. Aggregation
Aggregation is a process that represent a relationship between a whole object and its
component parts.
It abstracts a relationship between objects and viewing the relationship as an object.
it is a process when two entity is treated as a single entity.
In the example, the relation between College and Course is acting
as an Entity in Relation with Student. In the diagram above, the
relationship between college and Course together, is acting as an
Entity, which is in relationship with another entity student. Now in
real world, if a student visits a college, he/she will never enquire
about the college only or just about the course, rather he/she will
ask enquire about both.
11
Category or Union
Category represents a single super class or sub class relationship with more than one
super class.
It can be a total or partial participation.
For example Car booking, Car owner can be a person, a bank
holds a possession on a Car) or a company. Category (sub
classOwner is a subset of the union of the three super
classes Company, Bank, and Person. A Category member
must exist in at least one of its super classes.
12
Generalization and Specialization
These are very common relationships found in real entities .However, this kind of
relationship was added later as an enhanced extension to the classical ER model.
Specialized classes are often called subclass while a generalized class is called a
s

[@TAMIZHSELVANM-y3m]

Python full course video podunga nanba

[@desh_29]

Anna chuma padikadhinga Clear ah explain pani podunga

[@rabbitgaming4282]

Crystal❤️explain bruhhhh!!!!!!

[@Raj_S01]

I'm requesting you to please speak in English. Many north Indian students doesn't understand ur language including me also .