Entity Relationship Model

(ERM) is a data model that describes relationships among entities at the conceptual level with the help of ER diagrams.

Entity Relationship Diagram

is a diagram that depicts an entity relationship model’s entities, attributes, and relations.

rectangle

An entity is represented in the ERD by a

entity instance or entity occurrence

Each row in the relational table is known as an

entity set

A collection of similar entities is known as an

Relationships

describe associations among data.

connectivity

The type of relationship between entities is called

Chen notation

Relationships are represented by a diamond connected to the related entities through a relationship line. The relationship name is written inside the diamond.

Crow's Foot notation

Entities are connected by lines, and symbols at either end describe the cardinality of the relationship between the entities.

attributes

Each entity consists of a set of __ that describes particular characteristics of the entity.