Question

我有两个表订单和订单项。订单表具有ID，order_total，receiveved_amount orderitems表具有id，order_id，名称，total_item

我想要订单表中的receved_amount的总和，order_total以及订单项的total_item的总和。所以我用

SELECT SUM(`received_amount`) as totalRecieved,
       SUM(`order_total`) as orderTotal
FROM   `orders` AS `Order`
LEFT JOIN `order_items` AS `OrderItems`
       ON (`OrderItems`.`order_id`=`Order`.`id`)

和

SELECT SUM(`received_amount`) as totalRecieved,
       SUM(`order_total`) as orderTotal
FROM   `orders` AS `Order`
LEFT JOIN `order_items` AS `OrderItems`
       ON (`OrderItems`.`order_id`=`Order`.`id`)
group by order.id

但是他们都没有给我正确的结果。

Answer 1

您正在聚合数据层次结构的两个级别。对于每个订单，这都会导致笛卡尔积的问题。

解决方案是在进行order_items之前，先在join 上进行聚合：

SELECT SUM(received_amount) as totalRecieved, 
       SUM(order_total) as orderTotal
FROM orders o LEFT JOIN
     (SELECT oi.order_id, SUM(total_items) as total_items
      FROM order_items oi
      GROUP BY oi.order_id
     ) oi
     ON oi.order_id = o.id;

Answer 2

作为替代方案，您可以受益于cte结构或如下所示的临时表：

;with cte (order_id, SumTotalItems) as (
  SELECT oi.order_id, SUM(total_items) as SumTotalItems
  FROM order_items oi
  GROUP BY oi.order_id
)
select sum(o.receivedamount) as SumReceivedAmount
     , sum(o.order_total) as SumOrderTotal
     , cte.SumTotalItems
from orders o
left outer join cte on o.id = cte.order_id

来自带有联接的单个表的SQL总和

2 个答案: