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
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