3

我试图通过一个 SQL 查询来获得 5 个不同表中结果的总和。我有 5 个表，每个表可能包含属于订单的记录。5 个表中所有记录的总和决定了总订单价格。

在这个论坛上搜索我想出了以下查询：

SELECT
  OrderTotal.total + Shipping.amount + Service.amount - Gift.amount - RMA.total as TotalCosts
FROM
  (SELECT SUM(price * amount) AS total FROM order WHERE order_id=123456) OrderTotal
  (SELECT amount FROM shipping WHERE order_id=123456) Shipping,
  (SELECT amount FROM service WHERE order_id=123456) Service,
  (SELECT SUM(price * amount) AS total FROM rma WHERE order_id=123456) RMA,
  (SELECT amount FROM gift WHERE order_id=123456) Gift

我现在面临的问题是，例如，当最后一个 SELECT 返回 0 行时，不返回总 TotalCosts 。

如何解决这个问题？

4

2 回答 2

1

如何使用UNION？

SELECT  order_id, SUM(total) GrandTotal
FROM
        (
            SELECT  order_id, SUM(price * amount) AS total 
            FROM    `order` 
            WHERE   order_id = 123456
            UNION ALL
            SELECT  order_id, amount AS total 
            FROM    shipping 
            WHERE   order_id = 123456
            UNION ALL
            SELECT  order_id, amount AS total 
            FROM    service 
            WHERE order_id = 123456
            UNION ALL
            SELECT  order_id, SUM(price * amount) AS total 
            FROM    rma 
            WHERE   order_id = 123456
            UNION ALL
            SELECT  order_id, amount AS total 
            FROM    gift 
            WHERE   order_id=123456
        ) subTable
GROUP   BY order_id
于 2013-03-11T16:07:57.223 回答
0

您可以使用IFNULL函数来解决

SELECT
  IFNULL(OrderTotal.total,0) + IFNULL(Shipping.amount + IFNULL(Service.amount - IFNULL(Gift.amount,0) - RMA.total as TotalCosts
FROM
  (SELECT SUM(price * amount) AS total FROM order WHERE order_id=123456) OrderTotal
  (SELECT amount FROM shipping WHERE order_id=123456) Shipping,
  (SELECT amount FROM service WHERE order_id=123456) Service,
  (SELECT SUM(price * amount) AS total FROM rma WHERE order_id=123456) RMA,
  (SELECT amount FROM gift WHERE order_id=123456) Gift
于 2013-03-11T16:48:33.667 回答