运行总共连接两个表

Question

我有两张桌子

-----Dates-----          ------Sales------
Date    | Month          Date    | Quantity
---------------          ------------------
09/06/16| Jun            09/06/16| 2
09/07/16| Jul            15/07/16| 11
19/09/16| Sep            19/09/16| 12
21/09/16| Sep            09/07/16| 33
17/11/16| Nov            21/09/16| 45

我需要编写一个 SQL 查询来计算运行每个月的总销售额

我可以这样做吗？

SELECT Month,
(SELECT SUM(Quantity) FROM Sales WHERE Month<=Dates.Month)
FROM Dates, Sales
WHERE Dates.Date = Sales.Date
ORDER BY Month

感觉自己的思路有问题，但是没有数据库可以证明

Answer 1

您可以使用月份进行联接，然后对总数进行求和和分组

  SELECT month(d.date),  SUM(s.Quantity)
  FROM Dates  d 
  LEFT JOIN  Sales S on month(d.date) = month(s.date)
  ORDER BY month(d.date)

Answer 2

您可以使用 INNER JOIN 和 GROUP BY :

SELECT Dates.Month, SUM(Quantity)
FROM Dates INNER JOIN Sales ON Dates.Date = Sales.Date
WHERE   Sales.Month <= Dates.Month
GROUP BY Dates.Month
ORDER BY Dates.Month

Answer 3

试试这个，应该有效：

WITH CTE
AS
(
Select DateName(mm,D.Date) as Month,MONTH(D.Date) as UsedByOrderByLater,Sum(S.Quantity) as SumForCurrentMonth
 FROM Dates as D
    Inner Join Sales as S
    ON S.Date = D.Date
Group by DateName(mm,D.Date),MONTH(D.Date)
)
Select CTE.Month,CTE.SumForCurrentMonth ,
SUM(CTE.SumForCurrentMonth) OVER(Order by CTE.UsedByOrderByLater
ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) as runningtotal
from CTE

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