PHP / MYSQL中的类别？ [关闭]

Question

I try to create a menu system and within that menu show whatever there is in MySQL based on one column!

Example

Currently, I can add products from my admin panel and it will be added into MySQL database. When I add a product, I can give this product a brand name i.e. diesel, levi, etc.

Question 1

Now I know how to show the contents of the database in MySQL in a PHP file by using SELECT brand FROM products ..., but this will show all the duplicated brands in my menu (e.g. 3 levi's, 6 diesels) and it will show them like:

levi
levi
levi
Diesel
Diesel
Diesel
Diesel

But I only 1 need of each. How can I do that?

Question number 2

How can I link the diesel category only to products that have that brand? For instance, if someone clicks on the diesel category, php will only show products that have the diesel brand.

Answer 1

These are fairly simple relational database questions.

1; Use DISTINCT with your query like

SELECT DISTINCT `brand` FROM `products`;

2; You would need to use a WHERE clause, based on a parameter that you pass into category.php somehow. We can't really help you without existing code, but this should probably be what a file like category.php would be doing anyway.

That said, your brands should really be contained within a separate table and linked to from your products (probably one-many relation, one product can have one brand but a brand can have many products). You should really look up some database design concepts before continuing with your project, in my opinion.

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Here's a very simple diagram of how your relationship would work:

Rather than querying products for your brands, you would simply SELECT name FROM brand to get a list of your brands.

Then, passing in your brand_id to category.php, you can get the products like so SELECT * FROM product WHERE brand_id = 1.