I'm trying to design an ER diagram in the relational database module of my course. We were given a scenario to draw a diagram for and then create a database within Access. I have the database covered, but want to be sure I'm on the right track for the diagram.


The model is for business functions within a car dealership. Minimum and maximum cardinalities must be indicated. Entities and processes to be considered include Customer; Cash Received; Cash; Salesperson; AR Clerk; Sell Vehicle; Inventory.

A few assumptions must be made about resources and the payment event. Assume the company only sells inventory that is in stock, thus customers will not be ordering vehicles and every sale is only for one vehicle. Inventory is categorized based on model information. Additionally, assume that the dealership has multiple cash accounts and that customer payments are always deposited in the same cash account. Since the dealership offers financing, customers can make monthly payments on their vehicles so customers can buy now and pay in installments later. Any other assumptions that need to be made should be consistent with the business processes in a typical auto dealership.

My answer (I don't believe I have a firm grasp on this at all -- I also don't have the ability to embed pictures yet):


Thank you in advance for your help!!

1 Answer 1


Is that the whole problem statement? How come AR Clerk, Salesperson, etc are not described anywhere? You shouldn't just include only the entities listed. The italicized paragraph contains more entities and processes that should be modeled.

You can't have 2 Customer entities in the diagram. Draw another line from Customer to Receive Cash if you need to. You should use a few sentences to define each entity so others know what you intend them to be.

  • Thanks so much for your feedback! I'll make the adjustment to only have one Customer entity. I wish I had more information on the entities themselves; there is a lengthy sample dialogue between managers, but none that really provides any information on the entities; rather it is information pertinent to the build of the database in Access. The bulk of the information on what is expected from the ERD is in the italicized section. Much is (unfortunately) left up to interpretation based on a basic understanding of how a dealership might be run. Sep 17, 2020 at 23:18

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