Entity-Relationship (ER) Model

- Niraj Acharya
  • Developed by Peter Chen in 1976
  • Used for conceptual design of database
  • High-level conceptual data model
  • Not specific to any particular DBMS
  • Used for designing relational database

ER Model - Basic Concepts

  • Entity: Real-world object distinguishable from other objects
  • Entity Set: Collection of similar entities
    • Each entity set has a key
  • Relationship: Association among two or more entities
    • Relationship set
  • Attribute: Property of an entity or relationship type
    • Attribute set

Steps to build an ER Model

  1. Identify entities
  2. Identify relationships
  3. Identify attributes

Representation of different components of ER Model

Entity
Attribute
Relationship

Types of Attributes

  • Simple
  • Composite
  • Single-valued
  • Multi-valued
  • Derived

Weak and Strong Entity Set

Types of Relations

One to One

One to Many

Many to One

Many to Many

Types Of Participation

Total Participation

Partial Participation

Drawing a ER diagram from scratch

Any queries ?