亲子关系 [英] parent child relations

问题描述

选择父类别时将产品分配到子类别的最佳方法是什么?

What is the best way of getting products assigned to child categories when the parent category is selected?

即如果我选择顶级类别，我希望获得所有子类别中的所有产品，而不仅仅是分配到当前所选级别的产品.

i.e If I select the top level category I'd like to get all the products in all the sub categories not just products assigned to the current level selected.

因此选择类别 1 将返回 prod_id 的 1 和 2.选择类别 2 将返回 prod_id 2.

so selecting category 1 will return prod_id's 1 and 2. Selecting category 2 will return prod_id 2.

**category**
id parent_id name
1     0       Vegetables
2     1       Tomatoes
3     2       Yellow Tomatoes

**product_category**
prod_id cat_id
  1       1
  2       3

**products**
prod_id name
  1       Carrot
  2       Small Yellow Tomato

推荐答案

这个查询是您要查找的吗?

is this query what you're looking for?

$query =<<<MYSQL
 SELECT `prod_id`
 FROM `produdct_category` 
  INNER JOIN `category` ON `product_category`.`cat_id` = `category`.`id`
 WHERE `category`.`parent_id` = {$selectedParentId}
MYSQL;

更新的问题，更新的答案:

Updated question, updated answer:

$query =<<<MYSQL
 SELECT *
 FROM `produdcts` 
  INNER JOIN `produdct_category` ON `products`.`prod_id` = `produdct_category`.`prod_id`
  INNER JOIN `category` ON `product_category`.`cat_id` = `category`.`id`
 WHERE `category`.`id` = {$selectedCatId}
   OR `category`.`parent_id` = {$selectedCatId}
MYSQL;

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