PHP / MYSQL是否需要SQL加入？

Question

I know this may be a stupid question but I am not very experienced with SQL Joins and I don't want to do it without fully knowing that it is the right thing to do.

I have created a recipe site which have different categories like bread, biscuits, cake etc. these are all in the category table of the database. I have recipes in the recipe table.

The problem I am facing is, on the category page, since each category has its own ID I created one page where each categories redirect to and used this code

<a href="index.php?p=selected&id=<?php echo $recipe['cat_id']; ?>">

This one page features different categories based on the ID, the id is changed in the url so for the bread category it would look like this:

index.php?p=selected&id=1

So, since there is one page for each category I want it to display the recipes, I used this code:

$query = "SELECT * FROM recipes ORDER BY recipe_id ASC";

but this displays every recipe in the database, what I want is for it to display the recipe based on the category it is in like below:

$query = "SELECT * FROM recipes WHERE cat_id = :id ORDER BY recipe_id ASC";

The cat_id is part of the category table, so do I need to join this table to the recipe table to make it work?

Be sure to tell me if I have missed something,

Thank you for your time.

Answer 1

yes you have missed something must add column cat_id in recipes table which equal cat_id in category table when you add item in recipes table and then it simple

$query = "SELECT * FROM recipes
WHERE recipes.cat_id = :id";

or

$id = intval($_GET['id']);
$query = "SELECT * FROM recipes
WHERE recipes.cat_id = $id";

Answer 2

If one recipe one category then,

SELECT * FROM recipes inner join category
on category.id=recipe.cat_id
 where cat_id = :id ORDER BY recipe_id ASC";

If one cateory many recipes then

 SELECT * FROM recipes leftjoin category
    on category.id=recipe.cat_id
     where cat_id = :id ORDER BY recipe_id ASC";