加入第二个表时总和不正确

Question

这是我第一次请求你的帮助,

实际上我必须创建一个查询,并为它做了一个类似的例子.我有两张桌子,

Report (ReportID, Date, headCount)
Production(ProdID, ReportID, Quantity)

我的问题是使用此查询,我得到了错误的结果,

SELECT    
    Report.date, 
    SUM(Report.HeadCount) AS SumHeadCount, 
    SUM(Production.Quantity) AS SumQuantity
FROM         
    Report 
INNER JOIN
    Production ON Report.ReportID = Production.ReportID
GROUP BY
    Date
ORDER BY
    Date

我想有些行不止一次,请你帮个忙吗？

编辑

如果我运行查询以获得按天分组的人数总和,我得到:

  date        Headcount
7/2/2012    1843
7/3/2012    1802
7/4/2012    1858
7/5/2012    1904

我也得到了生产数量:

2012-07-02  8362
2012-07-03  8042
2012-07-04  8272
2012-07-05  9227

但是当我结合两个查询时,我得到的是假的,我预计7月2日8362数量对1843年,但我得到:

 day      TotalHeadcount    totalQty
7/2/2012    6021    8362
7/3/2012    7193    8042
7/4/2012    6988    8272
7/5/2012    7197    9227

Answer 1

使用以下方式对每个日期的记录进行分组

SELECT ReportSummary.ReportDate, SUM(ReportSummary.SumHeadCount) AS SumHeadCount, SUM(ProductionSummary.SumQuantity) AS SumQuantity
FROM
(
  SELECT Report.ReportDate, SUM(Report.HeadCount) AS SumHeadCount
  FROM Report 
  GROUP BY Report.ReportDate
) AS ReportSummary
INNER JOIN
(
  SELECT Report.ReportDate, Sum(Production.Quantity) AS SumQuantity
  FROM Production
  INNER JOIN Report 
  ON Report.ReportID = Production.ReportID
  GROUP BY Report.ReportDate
) AS ProductionSummary
ON ReportSummary.ReportDate = ProductionSummary.ReportDate
GROUP BY ReportSummary.ReportDate
ORDER BY ReportSummary.ReportDate