如何计算select语句列中其他表的总值

Question

我有三张桌子：

• CustOrder ： id, CreateDate, Status

• DenominationOrder ： id, DenID, OrderID

• 面额 ： id, amount

我想基于所有这些表创建一个视图，但是应该有一个额外的列，即Total应该可以计算每个订单金额的总和。

例如

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

可能吗？

Answer 1

我试着猜测你的表关系（以及数据，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

尝试这个：

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

DEMO

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

DEMO使用CTE