Question

名为库存的表1包含列商品
名为 Products_sold 的表2包含项目，数量
名为 products_purchased 的表3包含项目，数量

我需要获得三列的sql查询，例如

（产品）（表1中的所有项目）
（已售出产品）（product_sold表中每个项目的数量总和）
（购买的产品）（product_purchased表中每个项目的数量总和）

我有查询，但无法正常使用

  Select stock.Items as Products, 
         SUM(Products_sold.Quantity) as [Products Sold], 
         SUM(Products_purchased.Quantity) as [Products purchased]
  From 
         (
           (Stock LEFT JOIN products_purchased ON stock.Items=products_purchased.Items) 
           LEFT JOIN products_sold ON stock.Items=products_sold.Item
         )
  Group By stock.Items

Answer 1

试试这个：

SELECT S.Items as Products, 
       COALESCE(PS.Quantity, 0) as [Products Sold], 
       COALESCE(PP.Quantity, 0) as [Products purchased]
From Stock S 
LEFT JOIN (SELECT Items, SUM(Quantity) AS Quantity 
           FROM products_purchased 
           GROUP BY Items
         ) AS PP ON S.Items = PP.Items 
LEFT JOIN (SELECT Items, SUM(Quantity) AS Quantity 
           FROM products_sold 
           GROUP BY Items
         ) AS PS ON S.Items = PS.Items;

MySQL查询选择，SUM，LEFT JOIN

1 个答案: