如何计算每年售出的产品总数？

Question

我有3张桌子：

1. 产品（具有产品ID，价格等）
2. 订单（具有订单ID，日期等）
3. orders_products（具有详细的订单信息，例如产品数量等）

我想计算每年销售的产品总数。为此，我编写了以下查询：

SELECT YEAR(`o`.`date_purchased`) AS year,
       SUM(`op`.`products_quantity`) AS TotalUnits,
       `p`.`products_id`,
       `p`.`products_price` AS price,
       ( SUM(`op`.`products_quantity`) * `p`.`products_price` ) AS TotalAmount
FROM   `orders` AS `o`
       INNER JOIN `orders_products` AS `op`
               ON `o`.`orders_id` = `op`.`orders_id`
       INNER JOIN `products` AS `p`
               ON `op`.`products_id` = `p`.`products_id`
GROUP  BY `p`.`products_id`
ORDER  BY year

它给了我以下结果集：

它给出了按产品分组的总金额。但我想改为按年份分组总金额。

因此，对于2016年（以及其他年份），我希望得到以下结果：

2016     10,606 (since 6478 + 632 + 2072 + 1424)

但是我无法计算按年分组的总金额，因为每种产品的价格都不同。那么如何修改现有查询以获取每年售出的产品总数？

如果仅靠MySQL无法实现，那么我会毫不犹豫地使用PHP。

Answer 1

您只需要将数量和价格的乘积带到SUM中，以便每种产品的数量乘以其自己的价格：

SELECT YEAR(`o`.`date_purchased`) AS year,
       SUM(`op`.`products_quantity`) AS TotalUnits,
       SUM(`op`.`products_quantity` * `p`.`products_price`) AS TotalAmount
FROM   `orders` AS `o`
INNER JOIN `orders_products` AS `op` ON `o`.`orders_id` = `op`.`orders_id`
INNER JOIN `products` AS `p` ON `op`.`products_id` = `p`.`products_id`
GROUP  BY year
ORDER  BY year