I'm currently working on a school project on making a database for a grocery store. This is the original database design http://i.imgur.com/CK83O.png I'm sorry about the crude drawing, I had to translate it to English for this post and paint was the fastest alternative :P

When I met my teacher she asked about the design, for example she asked how you would look up which supplier was linked to a order. She also asked how you would get information about a product and supplier through the Order ID (Oid).

I'm having a bit of trouble understanding the basic design principles of databases. The story behind my database design is that my store wants to order products from suppliers. A bill is then created.

How can I make my design better? I would very much appreciate a explanation as well, to help me understand better, and to be able to explain why I designed my database as I did. Thank you VERY much in advance if you help me! You would really be an .