从产品和供应商那里获得最低价格

Posted 2023-03-17

【中文标题】从产品和供应商那里获得最低价格

【英文标题】：Get the lowest price from a product and the provider for that price

【发布时间】：2021-05-03 08:09:45

【问题描述】：

我正在查询一项学校作业，其中我选择了低于最低库存的产品，然后我选择了以最低价格提供每种产品的供应商。 这些是桌子。 +------------+     +------------------+     +------------+ | products |     | product_overview |     | provider | +------------+     +------------------+     +------------+ | productID |     | productID |     | providerID | | name |     | providerID |     | name | | stock |     | price |     +------------+ | min_stock |     +------------------+ +------------+ 这是我目前所拥有的。

SELECT p.name, pr.name
FROM products p JOIN product_overview po ON p.productID = po.productID
JOIN provider l ON po.providerID = pr.providerID
WHERE p.stock < p.min_stock
GROUP BY po.productID
ORDER BY p.name;

我寻找哪些产品有stock < min_stock，然后寻找供应商。目前，输出中给出的供应商并不是以最低价格交付产品的供应商。

【参考方案1】：

最简单的方法是使用窗口函数：

SELECT pp.*
FROM (SELECT p.name as product_name, pr.name as provider_name,
             ROW_NUMBER() OVER (PARTITION BY p.productID ORDER BY po.price ASC) as seqnum
      FROM products p JOIN 
           product_overview po
           ON p.productID = po.productID JOIN
           provider pr
           ON po.providerID = pr.providerID
      WHERE p.stock < p.min_stock
     ) pp
WHERE seqnum = 1
ORDER BY p.name;

【参考方案2】：

你可以使用not exists如下：

SELECT p.name, pr.name provider_name, po.price
  FROM products p JOIN product_overview po ON p.productID = po.productID
  JOIN provider pr ON po.providerID = pr.providerID
 WHERE p.stock < p.min_stock
   AND not exists 
      (select 1 from product_overview poo 
        where poo.productID = po.productID 
          and poo.price < po.price)