Chapter 12 What is ERD and Types Explain in Details

CHAPTER 12

ERD

(ENTITY RELATIONSHIP DIAGRAM )

ER-Model :- ER- Model Stand for entity relationship model.

It is a graphical approach for designing a database, It’s database modelling technique that generated an abstract diagram of system data and that diagram is used in designing a relational database. It was developed by Peter Chen in 1976.

ERD:- ERD stands for Entity Relationship Diagram, The Diagram generated by ER-Model is known as ERD. ERD show the relationship of different entities stored in the database.

Customer

Name	Address
Shailesh	India / 23333
Chu So Shang	South Korea/ 33322

Product/ Item

Name	Price
Mouse	250/-
Keyword	750/-

ER Diagram explains the logical structure of database, at last an ERD is implemented as a database. It helps us to analyze data requirements systematically to produce a well design database. It is considered as a best practice to completed ER Modelling before implementing your database.

ER diagram are based on three basic concepts entities, attributes and relationship.

1.) Entity :-An Entity is a real world object or concept about which your want to store information, An Entity can be place, person, object, or a concept etc. (as a Noun )

a.) Persons :- Students, Employees, Patient..

b.) Place :- Building, store..

c.) Object :- Car, Bike, Product..

d.) Concept :- Course (BCA, BBA, B-Tech, MBA..)

2.) Attributes :- An attributes are the properties or characters of an entity, It describes an entity, it is represented using oval shape.

3.) Relationship :- It specifies how entities are associated with each other. It is represented using diamond shape.

Important and uses of ERD:-

Database Design

Database debugging

Problem in requirement gathering

Entity Types :-

1.) Strong Entity :- An Entity which does not depends on any other entity to exits is called Strong entity .

Ex:- Employees

2.) Weak Entity :- An Entity Which depends on other entity to exist is called weak entity.

Ex :- Loan

Attribute Types :-

a.) Single value attributes

b.) Multi-value attributes

c.) Simple attributes

d.) Composite attributes

e.) Derived attributes

f.) Key attributes

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