递归 select 并加入相关 table

Question

CREATE TABLE IF NOT EXISTS "product_category"(
  "id" SERIAL NOT NULL,
  "parent_id" integer DEFAULT NULL,
  "name" varchar DEFAULT NULL,
  PRIMARY KEY ("id")
);


CREATE TABLE IF NOT EXISTS "product"(
  "id" SERIAL NOT NULL,
  "product_category_id" integer DEFAULT NULL,
  PRIMARY KEY ("id")
);

我有两个像上面的table，
product_category 是层次结构，
和 product.product_category_id fk product_category.id。

如何 select 特定 product_category id 下的所有产品，

例如
如果输入 product_category 1,
输出 -> product:1, product:2

如果输入product_category 2
输出 -> product:2

product_category
id | parent_id | name
1  |           | parent
2  | 1         | child
3  | 2         | child child


product
id | product_category_id
1  | 1
2  | 3

查询

像这样??但是这个 return 只有 product_category 列表....我想要产品列表

WITH RECURSIVE pc AS (
  SELECT pc.id AS id
    FROM product_category pc

    LEFT JOIN product p ON p.product_category_id = pc.id

    WHERE id =  

  UNION ALL

  SELECT child.id
    FROM product_category AS child

    LEFT JOIN product p ON p.product_category_id = child.id

    JOIN pc ON pc.id = child.parent_id 
)
SELECT * FROM product_category WHERE id IN (SELECT * FROM pc)

Answer 1

注意：我的系统上没有安装 postgresql，所以我是基于概念来讨论的。我没有看到你在哪里定义了外键约束......我仍然假设你已经这样做了。而且我还没有检查 CTE/Common Table 表达式的正确性（- 基本上是 SQL 的递归部分）。 假设 CTE 是正确的 -

更换怎么样

SELECT * FROM product_category WHERE id IN (SELECT * FROM pc)

与

SELECT * FROM product WHERE product_category_id IN (SELECT * FROM pc)

CTE 的正确性是我接下来要检查的事情。

所以显然以下应该有效：

;
WITH RECURSIVE pc AS (
    SELECT pc.id AS id
    FROM 
    product_category pc
    LEFT JOIN product p 
    ON p.product_category_id = pc.id
    WHERE pc.id = <Your product category id of interest>
    UNION ALL
    SELECT child.id
    FROM 
    product_category AS child
    LEFT JOIN product p 
    ON p.product_category_id = child.id
    JOIN pc 
    ON pc.id = child.parent_id
)
SELECT id as product_id FROM product WHERE product_category_id 
IN (
   SELECT * FROM pc
);

Answer 2

您应该首先建立类别列表，然后将其加入产品。

WITH RECURSIVE pc AS (
  SELECT id
  FROM product_category 
  WHERE id = $id

  UNION ALL

  SELECT child.id
    FROM product_category AS child
    JOIN pc ON pc.id = child.parent_id 
)
SELECT pr.*
FROM product pr
  JOIN pc on pr.product_category_id = pc.id
;

递归 select 并加入相关 table

recursive select and join related table

sql

database

postgresql

recursive-query