Question

我有一个表格，其中包含

形式的库存

ID |Product ID | Movement |  Cumulative Quantity | Store ID
=================================================|=========
1  | 1         |  100     |  100                 |  1 
2  | 1         |  -4      |  96                  |  1
3  | 1         |  -1      |  95                  |  1
4  | 2         |  100     |  100                 |  1
5  | 1         |  100     |  100                 |  2

每一行基本上都有一个库存移动，最后一行MAX（ID）包含cumulative_quantity，其中包含可用库存

另一个包含产品的表

ID | Product Name
====================
1  | Apple Juice
2  | Orange Juice

我正在寻找

形式的输出

Product ID | Product Name | Total Quantity at all stores
========================================================
1          | Apple Juice  | 195
2          | Orange Juice | 100

这是下表的简化版

Store ID   | Product ID | Product Name | Cumulative Quantity
========================================================
1          | 1          | Apple Juice  | 95
1          | 2          | Orange Juice | 100
2          | 1          | Apple Juice  | 100
2          | 2          | Orange Juice | 0

Answer 1

这是一个相对简单的SUM()聚合，JOIN。 SUM(Movement)将导致所有商店的总数量。

SELECT
  inventories.productId,
  productName,
  SUM(Movement) AS `Total Quantity`
FROM inventories JOIN  products ON inventories.productId = products.productId
GROUP BY inventories.productId, productName

Answer 2

有几种方法可以做到这一点

使用MAX

在From子句中进行子查询

SELECT products.id as `Product ID`,  
       products.`Product Name`, 
       SUM(inventory.`Cumulative Quantity`) as Total Quantity at all stores
FROM products
     INNER JOIN inventory
     ON products.`id` = inventory.`id`
     INNER JOIN 
     (
     SELECT ( max(`id`)  as `id`,
              `product id`,
              `store id`
     FROM 
           `inventory`
     GROUP BY
              `product id`,
              `store id`) maxinventory
     ON inventory.`id` = maxinventory.`id`
GROUP BY
      products.`id`,  
       products.`Product Name`

这是另一个使用IN

SELECT products.id as `Product ID`,  
       products.`Product Name`, 
       SUM(inventory.`Cumulative Quantity`) as Total Quantity at all stores
FROM products
     INNER JOIN inventory
     ON products.`id` = inventory.`id`
WHERE
      inventory.`id ` IN
     (
     SELECT ( max(`id`)  as `id`,
     FROM 
           `inventory`
     GROUP BY
              `product id`,
              `store id`) 
GROUP BY
      products.`id`,  
       products.`Product Name`

Answer 3

诀窍是使用子查询来查找当前的库存记录，即每个id对的最大product_id, store_id个库存记录：

SELECT
  product_id, name, SUM( cumulative_qty ) AS total_qty
FROM
  (SELECT MAX(id) AS id FROM inventories GROUP BY product_id, store_id) AS cur
  NATURAL JOIN inventories
  JOIN products ON products.id = inventories.product_id
GROUP BY product_id

（顺便说一句，我怀疑你想要inventories (product_id, store_id, id)上的索引来使这个查询合理有效。当然我假设id列是主键。）

包含join的子查询的MySQL总和

3 个答案: