MYSQL 8 + : 查询查找类别下的产品，当类别在层次结构中并且产品附加到叶类别节点时

Question

Table：类别

id	name	parent
1	Electronics	null
2	TV	1
3	Portable	1
4	CRT	2
5	LCD	2
6	Plasma	2
7	Mp3 Players	3
8	CD Players	3
9	Flash	7

Table : products (products are attached to the leaf category id)

id	name	category_id
1	Flash Player	9
2	Samsung LCD TV	5
3	LG Plasma TV	6

生成 category_products 结果集的查询 ??

结果集：

id	product_id	category_id
1	1 (Flash Player)	9 (Flash)
2	1 (Flash Player)	7 (Mp3 Players)
3	1 (Flash Player)	3 (Portable)
4	1 (Flash Player)	1 (Electronics)
5	2 (Samsung LCD TV)	5 (LCD)
6	2 (Samsung LCD TV)	2 (TV)
7	2(Samsung LCD TV)	1 (Electronics)
5	3 (LG Plasma TV)	5 (PLasma)
6	3 (LG Plasma TV)	2 (TV)
7	3(LG Plasma TV)	1 (Electronics)

我们如何从 mysql 查询生成这个结果集？

Answer 1

WITH RECURSIVE
  recursive_membership AS
(
  SELECT
    p.id     AS product_id,
    p.name   AS product_name,
    c.id     AS category_id,
    c.name   AS category_name,
    c.parent AS category_parent_id
  FROM
    products     p
  INNER JOIN
    categories   c
      ON c.id = p.category_id

  UNION ALL

  SELECT
    r.product_id,
    r.product_name,
    c.id,
    c.name,
    c.parent
  FROM
    recursive_membership   r
  INNER JOIN
    categories             c
      ON c.id = r.category_parent_id
)
SELECT
  product_id,
  product_name,
  category_id,
  category_name
FROM
  recursive_membership