sql - 如何计算select语句的一列中其他表的值的总和

Question

我有三张桌子：

• 客户订单：id, CreateDate, Status

• 面额顺序：id, DenID, OrderID

• 面额：id, amount

我想根据所有这些表创建一个视图，但应该有一个额外的列，即Total应该在那里可以计算每个订单金额的总和。

例如

• 订单 1 总面额 3，总金额 = 250+250+250=750
• 订单2总面额2，总金额=250+250=500

是否可以？

Answer 1

我试着猜测你的表格关系（还有数据，你没有提供任何样本）：

SELECT co.id, 
       COUNT(do.DenID) AS `Total denominations`, 
       SUM(d.amount) AS `Total amount`
FROM CustOrder co
INNER JOIN DenominationOrder do ON co.id = do.OrderId
INNER JOIN Denomination d ON do.DenId = d.id
GROUP BY co.id

Answer 2

试试这个：

SELECT o.CreateDate, COUNT(o.id), SUM(d.amount) AS 'Total Amount' 
FROM  CustOrder o 
INNER JOIN DenominationOrder do ON o.id = do.OrderID
INNER JOIN Denomination      d  ON do.DenId = d.id
GROUP BY o.CreateDate

演示

另一种方法是使用CTE，如下所示：

;WITH CustomersTotalOrders
AS
(
    SELECT o.id, SUM(d.amount) AS 'TotalAmount' 
    FROM  CustOrder o 
    INNER JOIN DenominationOrder do ON o.id = do.OrderID
    INNER JOIN Denomination      d  ON do.DenId = d.id
    GROUP BY o.id
)
SELECT o.id, COUNT(ot.id) AS 'Orders Count', ot.TotalAmount
FROM CustOrder o
INNER JOIN CustomersTotalOrders ot on o.id = ot.id
INNER JOIN DenominationOrder do ON ot.id = do.OrderID
INNER JOIN Denomination      d  ON do.DenId = d.id
GROUP BY o.id,  ot.TotalAmount

这会给你：

  id   |  Orders Count | Total Amount
-------+---------------+-------------
  1            3             750
  2            2             500

使用 CTE 的演示