5. Entity Relationship Diagrams

These relationships can be shown in the form of a diagram.

This diagram is known as an 'entity relationship diagram', E-R diagram or ERD

As part of your exam, you will probably have to either draw or interpret an E-R diagram. Before you can do this, you need to be able to interpret the relationships between the entities.


These relationships take the form of:

- one-to-one

- one-to-many

- many-to-many

We will look at each of these relationships in turn over the next few pages.


challenge see if you can find out one extra fact on this topic that we haven't already told you

Click on this link: Designing 1NF