Entity-Relationship model: Crow's foot notation example

In this episode, we’ll create an entity-relationship diagram using crow’s foot notation. We’ll keep things simple by leaving out the attributes and focusing on entities and relationships.
1. Open up the gleek.io app https://www.gleek.io and select the entity-relationship option from the dropdown.

2. Let’s use a very simple example of the relationship between a customer and an order.
Imagine that a customer places an order. The relationship is one and only one for the customer and zero or many on the order side.

3. The customer is now liable for an invoice. One and only one customer is liable for zero or many invoices.

4. The invoice covers an order. One and only one invoice covers one or many orders.

5. The customer has an address. One or many customers have one or many addresses. It’s like how you can add lots of different addresses to your Amazon account.
We show this is as an optional relationship with a dashed line. You can create a dashed line by adding a dot symbol in the connection syntax.

6. The customer’s address receives the order. One and only one address receives zero or many orders.
The order includes an item. One and only one order includes one or many items.

7. Each product can be ordered as one or many items. So zero or many items are ordered for one and only one product.

8. When it comes to categories, each product can be in one and only one category. But each category can include one or many products.

That’s all for our crow’s foot notation example for ER diagrams.
I hope this video has helped you understand how the different cardinality relationships work between entities.

You might need to go back and watch it again a couple of times.
Or even better – make sure you try it out on Gleek.io!

Don’t forget to give us your feedback in the comments, and subscribe for more tutorial videos.

Happy diagramming!