E-R Diagram

E-R Diagram -
It is combination of entities and relationship among those entities in a pictorial form for database.It is used at the time of database design,which makes easier to developer for understanding the database.

Entity can be defined as a thing or an object in a real word.

In otherwords,we can say entity is a set of attributes.

It is represented as rectangle.
Entity Set can be defined as collection of entites or a set of entites for a particular database.

Relationship can be defined as a relation between two or more entities.

In otherwords ,we can say that association between entities is known as relationship.

It is represented as diamond .
Relationship Set can be defined as collection of relationship or a set of relationship for particular database.

Common Notations Used in E-R Diagram are as follows -

Simple E-R Diagram for Hospital Management System can be showed as follows-