# Miscellaneous > Database Design >  Modeling ER Diagram (help with exercise)

## RandomGuy

Hey guys, how are you?
This is my first time on this site, nice to meet you!
I've been using databases for a long long time but i never created an ER Diagram before; i mean, i know about weak entities, attributes and everything related to that but i am not an expert. My teacher gave me and exercise, i did it but he told it was not correct; i am really frustrated about that  :Frown: .

Could you please tell me how would you draw this ER Diagram?
It goes like this:



> We work to build an e-commerce platform that facilitates B2C sales (company to consumer) and C2C (consumer to consumer).
> On our platform, anyone who wants to make a sale (be it a company or a person) has a registered user and a catalog of products that you can sell. They can be used or new. For each product that is published for sale, a definition is established general parameters (the same product may be published more than once with different payment options and / or promotions).
> Sellers who sell used products usually have a single unit, instead Sellers of new products generally handle varied stocks.
> The available stock of a product can be obtained by being connected to your system (this allows online update) or be manually maintained in our application. Each Seller maintains his own product catalog, with the name and details that he considers.
> Each product is in a category, which makes it easy to search, and can be related to other items (products). We use this a lot to cross sell (for example Someone who buys a battery may be interested in purchasing a charger)
> In the same purchase I can buy multiple products and / or quantities of each one while that it is the same seller.
> In case of acquiring multiple items the seller can pack them together (example if I buy 2 headphones) to simplify and cheaper shipping or otherwise, each item will have a different shipping (with a separate cost for each). For each shipment I will have an id of tracking / particular monitoring (this is done in the provider of the same, example Andreani).
> Each purchase has a single shipping address, even if they are divided into multiple packages.
> A buyer must always be logged in and for each of them we have their data personal, rating given by sellers for their purchases, accumulated points (which give you benefits) and we keep a record of your operations. With each of purchases made by our customers add points, which allow them to access
> ...


Can you help me?

Thanks! :Smilie:

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## Parker

Try this, RandomGuy:

http://www.parkershannon.net/eda/DataModel.html

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