Identifying Entities, Attributes, and Relationships in ERD

A Step-by-Step Guide to Structuring Your Data Model

Before you can design a database or draw an Entity-Relationship Diagram (ERD), you need to understand the building blocks: entities, attributes, and relationships.

In this guide, you’ll learn how to identify these elements from real-world requirements and how to organize them visually in an ERD—one of the most valuable skills for Business Analysts, System Analysts, and anyone working with data-driven systems.

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What Are Entities?

An entity is a thing, person, place, or event about which data needs to be stored.

How to Identify an Entity:

• It’s a noun in your requirements.

• It has distinct records.

• It’s important enough to track in the system.

🔍 Examples:

From a ride-sharing app:

• Driver

• Rider

• Trip

• Vehicle

Each of these is a separate thing we want to store data about.

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What Are Attributes?

An attribute is a property or characteristic of an entity. In a database, attributes become fields/columns.

How to Identify an Attribute:

• It describes or defines the entity.

• It answers questions like: “What do we want to know about this?”

Examples:

For the Driver entity:

• DriverID (Primary Key)

• Name

• LicenseNumber

• PhoneNumber

Tip: Every entity should have a primary key (PK)—a unique identifier for each record.

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What Are Relationships?

A relationship defines how two entities are connected. It describes interactions, associations, or dependencies.

How to Identify a Relationship:

• Look for verbs in your business rules.

• Ask: “How is Entity A connected to Entity B?”

Examples:

• A Rider books a Trip

• A Trip uses a Vehicle

• A Driver completes a Trip

Relationships can be:

• One-to-One (1:1)

• One-to-Many (1:N)

• Many-to-Many (M:N)

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Real-World Example: Food Delivery App

Let’s walk through an example to identify entities, attributes, and relationships.

Requirement:

"Customers place orders through the app. Each order includes one or more food items. Every order is delivered by a delivery person."

Step-by-Step Breakdown:

Entities:

• Customer

• Order

• Item

• DeliveryPerson

Attributes:

• Customer: CustomerID, Name, PhoneNumber

• Order: OrderID, OrderDate, TotalAmount

• Item: ItemID, Name, Price

• DeliveryPerson: DeliveryID, Name, VehicleType

Relationships:

• A Customer places an Order (1:N)

• An Order contains multiple Items (M:N)

• A DeliveryPerson delivers an Order (1:N)

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ERD View (Text Format)

[Customer] ────< places >──── [Order] ────< contains >──── [Item]
                                 │
                            delivered by
                                 │
                         [DeliveryPerson]

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Tips for Analysts

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Mastering how to identify entities, attributes, and relationships is the first step toward building effective databases and clear system designs.

With this skill, you can confidently:

• Convert user requirements into ERDs

• Communicate better with developers

• Ensure that the database supports real-world logic

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