Question

I am working on my school project to create an eCommerce website that sell and rent product.

My main problem is that I can’t find the best design for the “Renting” part. For now I am thinking about two designs:

The first database design suggestion:

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The second database design suggestion:

As you can see there are the same tables in both designs but with different relations, but I can’t tell which one is better.

I will be happy if you can tell me which design is better or if there is a better way to design my database altogether.

Answer 1

Think of your problem from the real-life perspective:

1. You will be offering “something”, being products in your schema;
2. You will be working with “somebody” or customers in your schema.

These 2 tables are most important, as without them the whole thing has no meaning.

Next, in real life, you have to have papers for each deal you’ll make in order to:

1. Report to authorities and pay taxes (don’t you like to pay taxes?);
2. Keep track of products that are “on hands” of your customers.

These are orders of 2 types: purchase and rent.

Note, though, that it is unlikelly to rent a set of products with different return dates in one order. Typically, one will rent a set of related items for some special case, like wedding celebration or bathroom repair. In case you need some products for 2 days while others for 2 weeks, it is better to create 2 orders, as different delivery conditions or discounts may apply.

Therefore I think that initial variant #1 matches your goal better with the following updates:

1. order_type column should be added to the orders table;
2. rent_details should relate to orders table;
3. rent_details should have only order_id in place of rent_detail_id + order_items_id;
4. it very necessary to have a separate price column in the order_items table along with discount;