如何正确构建数据库

Question

I've come to a problem with which I would like to ask you for some directions. I have database as in image below.

1 In my application I have products predefined, so they automaticaly popup in textbox, depends on first letter. My problem is that every product available in multiple colors. And i dont know how to make a proper table. Should i make one table only with colors?

2 Let's say Customer orders 5 monitors, and 4 keyboards that are all on same Order. Where should I have quantity? In my OrderProduct table?

3 What if customer want a custom sticker or his logo printed on item selected. If I select print on item or sticker in my application, where in database should this be stored? Also on OrderProduct?

Answer 1

1. Add a table called Colors and have it have the fields ID, Feasible Name, etc. In the Product show a bitwise value for the Colors it supports.

2. Yes, you would have the Quantity in the OrderProduct table.

3. It depends on what kind of stickers he is getting. Is the sticker going to be one he can pick from or is it something he can upload?

If your client is going to need to be able to customize each item, then you should have each item as a separate insert into the OrderProduct table and not have a quantity field- once you do that just have a reference to the sticker id which could be predefined or user defined.

Back to the colors- like I said if you're going to be able to customize each product then make a new insert for each product and remove a quantity column and then just add a ColorID column to the OrderProduct table where you will define what color or customization's that specific product would have.

---

Response to comment

The application needs to know what colors each item comes in, so you may have Black and Gray keyboards while having Black and Red monitors. A bitwise value is like a flag system except with numbers. Lets say you had...

1 | Black
2 | Gray
3 | Red

If a product could have Black and Gray you would do Black,Gray which goes to 1,2. If a product has Black and Red you would do Black,Red which goes to 1,3. All a bitwise value does is convert it to value that a computer can comprehend easier.

So to get the bitwise value for Black & Gray you square the ID and add it together (bor). Once you have that value (which is the bitwise value) you can run band on it to see if it has that color.

This is a really good tutorial on bitwise for PHP, I recommend reading it for more information on the topic.

Answer 2

1. The problem you describe - a "product" is available in multiple colors - is common; the standard solution is to introduce the concept of "product variant". For instance, T-shirts are available in multiple colors and multiple sizes; shoes are available in multiple sizes etc.

The database solution can vary; see this answer on SO for my recommendation if you don't know in advance what the variant types will be, or this if you do.

Depending on which solution you go with, you can then include the reference to the variant in the product_order table.

This solution allows you to extend the solution for future product types without polluting the "product_order" table - if you use @Hans's recommendation to include a bitmask to indicate colour, and you introduce size as another dimension, very quickly your "product_order" table starts to include a lot of knowledge of the product structure, and it becomes hard to manage/validate.

2. Yes, quantity is usually included in the order_product table (this is more commonly called "orderlines"). It's also a good idea to include the unit price - the price of the product may change over time, and you want to record the price the customer agreed to when placing the order.

3. For customizations, you may want to create an "order_customization" table, with a link to the order_product table, and the selected customization, eg

   OrderID ProductID Customization 1 2 Blue sticker 1 1 Green sticker

Presumably, not all items on an order would have customizations; if a single order_product line with a quantity > 1 could have different customizations for each item, you'd have to split it down even further...