Entity-Relationship Model

Entity-Relationship model is a type of database model based on the notion of real world entities and relationship among them. We can map real world scenario onto ER database model. ER Model creates a set of entities with their attributes, a set of constraints and relation among them.

ER Model is best used for the conceptual design of database. ER Model can be represented as follows :

● Entity - An entity in ER Model is a real world being, which has some properties called attributes. Every attribute is defined by its corresponding set of values, called domain.

● For example, Consider a school database. Here, a student is an entity. Student has various attributes like name, id, age and class etc.

● Relationship - The logical association among entities is called relationship. Relationships are mapped with entities in various ways. Mapping cardinalities define the number of associations between two entities.

● Mapping cardinalities:

○ one to one

○ one to many

○ many to one

○ many to many