Components of ER Model

Let’s go back to your café.
Now you’ve decided to organize things properly. You identify:

• Customers (who comes)
• Orders (what they buy)
• Items (what you sell)

But just listing them isn’t enough…
You also need details like customer name, order date, and how everything is connected.

This is where the components of the ER Model come into play; they break your system into clear building blocks.

Main Components

The ER Model has three main components:

1. Entity → Object (Student, Customer)
2. Attribute → Details (Name, ID)
3. Relationship → Connection (Enrolls, Places)

These three together form the complete structure of any database.

Entity

An Entity is a real-world object that we want to store data about.

Examples:

• Student
• Customer
• Product

It is represented by a rectangle in ER diagrams.

Code Example

Real Life Example

• In a college system, Student is an entity
• In a bank system, Customer is an entity

Attribute

An Attribute describes an entity (its properties).

Examples:

Represented by an oval

Code Example

Real Life Example

• Customer → Name, Phone Number
• Order → Date, Amount

Relationship

A Relationship shows how entities are connected.

Examples:

• Student enrolls in Course
• Customer places Order

Represented by a diamond

Code Example

Real Life Example

1. College System
   • Student → Enrolls → Course
2. E-commerce
   • User → Buys → Product
3. Bank System
   • Customer → Owns → Account