October 2, 2020

How to Draw Entity Relationship Diagrams (ERDs)

Diagrams for Software Engineering
IT Management

An ERD, or entity relationship diagram, is a type of flowchart that helps you clearly visualize your database design by showing how the "entities" in the system relate to one another.

To learn more about the basics of entity relationship diagrams, check out our blog, What is an ER Diagram? This ER diagram tutorial will cover how to make an ERD anywhere, with specific tips for using Gliffy's ERD tool for Confluence or online. Read on to learn how to make an ER diagram or jump ahead to one of the following sections:

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Why Draw an ER Diagram?

ERDs, also called ER diagrams or ER models, are used to describe data and how pieces of data interact with one another. For this reason, ERDs are extremely important in database design and projects that require a clear structure of all data — think of it as the standardized way to draw a database diagram. By applying this standard, your team can easily understand the structure of a database or the information you collect within your system.


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Video ER Diagram Tutorial: How to Draw a Database Diagram

Drawing entity relationship diagrams is easier if you choose to use online diagramming software. Check out Gliffy’s ER diagram tool for Confluence or start a free trial of Gliffy Online.


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How to Draw an Entity Relationship Diagram

There are a few basic steps to take to draw an ER diagram anywhere: in Gliffy, with Powerpoint, a whiteboard, or even on the back of a napkin. Here’s the basic order to follow.

1. Determine the Entities in Your ERD

Step one of drawing an ER diagram

Start by identifying the “what”s in your system or architecture. Entities are represented with a rectangle, and you’ll want to give them plenty of room so that you can add to your diagram in the next steps.

2. Add Attributes to Each Entity

Step two of how to draw an ER or database diagram

Next, consider the attributes that you need to describe each entity. These are drawn and labeled inside ovals. Connect these to the relevant entity and position your attributes to the outside of your diagram, which leaves room for relationships.

3. Define the Relationships Between Entities

Step three of drawing an ER diagram

Now, think through the relationships or verbs taking place within your system. The easiest way to do this is to look at each entity and try to connect it to another by saying, “What does the ___ do with the ___.” The customer purchases the phone. The cell service maintains the phone. The cell service creates a bill. The customer pays the bill. 

4. Add Cardinality to Every Relationship in your ER Diagram

Step four of how to draw an ERD

The final step for this simple ER diagram is to define the amount of data that will come from each entity. Cardinality is a simple notation that quickly tells your ERD reader whether there are zero, one, many, or some combination of those factors between each entity. Your customer can purchase one or many phones. The cell service maintains many phones. The customer pays one bill.

5. Finish and Save Your ERD

This is just a high-level ER diagram, but it provides enough detail that you should now have a teammate or partner check your work — if you're working in Confluence, you can even invite them to a real-time collaboration session. One of the best ways to check your work is to simply have them try to read your diagram out loud. If they end up telling a different story than you intended, you need to do some tweaking.

Another good step to take is to clean up or polish your diagram — if you were drawing by hand, you might have some stray eraser marks. Take a moment to finalize your diagram by aligning shapes, adding color, or redrawing lines to more clearly connect your entities, attributes, and relationships. All these steps are easy if you’re using an online diagramming tool like Gliffy!

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Why Draw Entity Relationship Diagrams With a Digital ERD Tool?

There are a few benefits to using software to complete the above steps and draw an entity relationship diagram. With Gliffy, you can create ERDs and:

  • Track changes and create versions of your diagrams
  • Generate ERDs from text with the Mermaid diagram editor
  • Draw ERDs with interactive layers that can be toggled on and off
  • Diagram with your team in real time
  • Use previous diagrams as a template for your next

You can give these features a try with a free trial of Gliffy for Confluence, but if your team doesn't use Confluence, you can create your ERD (and other types of application architecture diagrams!) in our online diagramming tool, Gliffy Online.


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