Question

选择父类别时，将产品分配给子类别的最佳方法是什么？

即如果我选择顶级类别，我想获得所有子类别中的所有产品，而不仅仅是分配到当前级别的产品。

所以选择类别1将返回prod_id的1和2.选择类别2将返回prod_id 2.

**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

Answer 1

这是您要查找的内容吗？

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

更新了问题，更新了答案：

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

Answer 2

更正表名并选择首先需要选择的字段。然后做这样的事情：

SELECT * FROM `products` AS p
INNER JOIN `product_category` AS pc ON p.id = pc.prod_id
INNER JOIN `category` AS c ON pc.cat_id = c.id
WHERE `parent_id` = YOUR_VALUE_HERE

父母关系

2 个答案: