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What is an entity relationship diagram (ERD)?
ERDs are used for describing data and the rules determining how entities and attributes interact with each other. An Entity-Relationship diagram is hugely important in database design and should be the first thing you draw when contemplating database architecture. (For a more in-depth look as well as a description of commonly used ERD symbols and their meaning, check out this article.)
How to draw an ERD diagram
To get started creating your ERD in Gliffy, an online ER diagram tool, open up a new diagram and scroll down to “more shapes” in the library section.
Select Software Design, open up all the options by clicking the down arrow, then choose the Entity-Relationship symbols.
Step 1: Start by determining the entities that will make up your diagram. In the case of this cell phone purchase flow, the entities are: the customer, the type of phone, the bill, and the login.
Step 2: Next, determine the attributes (or variations) your entities will have. For the customer, we’ll need to know name, customer id, their phone number, where they live and the amount they need to pay. Go through each of your entities and determine what attributes they need to have.
Pro Tip! To keep your ERD diagram neat, space your entities and attributes out out evenly and color-code them. You can color code multiple shapes at a time by selecting them.
Step 3: Determine what kind of relationships govern the interaction between different entities. Plot them out.
Step 4: Decide whether the interactions will be one to one, one to many, many to one etc. and choose the appropriate connectors. You can either select the appropriate connector types from the shape library or choose the appropriate tip type once your shapes are joined.
Once your diagram is complete, you can decide to share it and ask for collaborators to leave comments, print it or publish it via a public link.
