See How Systems and Data Connect at a Glance

As a Business Analyst, System Analyst, or anyone working with data, you need a way to visually map how data entities relate to each other. That’s where Entity-Relationship Diagrams (ERDs) come in.

ERDs are a powerful tool for planning, designing, and understanding databases. Whether you're working on a small app or a complex enterprise system, ERDs help ensure everyone—from developers to stakeholders—is on the same page.

What Is an ERD?

An Entity-Relationship Diagram (ERD) is a visual representation of data entities and the relationships between them. Think of it as a blueprint for your database—before any table or code is created.

ERDs are commonly used during:

Requirements gathering
Database design
System documentation
Communication between business and technical teams

Core Elements of an ERD

1. Entities

Entities represent real-world objects or concepts that have data stored about them.
Represented as rectangles.

Examples:

Customer
Order
Product

2. Attributes

Attributes are the data fields or properties of an entity.
Represented as ellipses or listed inside the entity.

Examples for Customer:

CustomerID
Name
Email

Primary Key (PK) – Uniquely identifies each record.
Foreign Key (FK) – Connects one entity to another.

3. Relationships

Relationships define how entities are connected to one another.
Represented as diamonds or just lines with labels (depending on the notation).

Examples:

A Customer places an Order
A Student enrolls in a Course

4. Cardinality

Cardinality shows how many instances of one entity can be related to another.

Type	Meaning
One-to-One (1:1)	Each entity has one match
One-to-Many (1:N)	One entity has many matches
Many-to-Many (M:N)	Many entities match many others

ERD Example (Text Version)

[Customer] ────< places >──── [Order]

Customer:
- CustomerID (PK)
- Name
- Email

Order:
- OrderID (PK)
- OrderDate
- CustomerID (FK)

This shows that one Customer can place many Orders, but each Order belongs to one Customer.

ERD Notations (Quick Note)

There are a few ways to draw ERDs:

Crow’s Foot Notation (most common for analysts and designers)
Chen Notation (uses diamonds for relationships)
UML Class Diagrams (used by developers)

For most business analyst work, Crow’s Foot is the clearest.

Why ERDs Matter for Analysts

Benefit	Why It’s Important
Clarifies business rules	Shows how entities are logically related
Improves communication	Visual models help teams align
Aids database design	Used by developers and DB architects
Reduces ambiguity	Makes data structure explicit

Tools to Create ERDs

You don’t need to be a designer—just use one of these:

Lucidchart (easy for collaboration)
Draw.io / Diagrams.net (free and flexible)
DBDiagram.io (code-based, quick to use)
MySQL Workbench (for developers)
ERDPlus (for students and quick diagrams)

Entity-Relationship Diagrams are one of the most valuable tools in a business analyst’s toolkit. They help you visualize structure, spot gaps, communicate clearly, and align business needs with database design.

You don’t need to know SQL to create ERDs—but by mastering ERDs, you’ll be better prepared to contribute to smarter, scalable systems.

Entity-Relationship Diagrams (ERD): A Visual Guide