如何显示每一行根据Sql中的持续时间计算日期

Question

我有两个表，其中一个表有开始日期，另一个表有持续时间。表格值如下

游

TourID  | StartDate | Tour Name     
  1     | 2016/5/10 | example name  
  2     | 2016/3/20 | Tour 2  

PlaceTrip

TripID   | Place ID   | Duration(days) | TourID
  1      |     1      |  5             | 1
  2      |     2      |  7             | 1
  3      |     3      |  2             | 1 
  4      |     1      |  10            | 2 
  5      |     2      |  4             | 2

预期/有用的查询结果是日期+持续时间=到达日期

 TourID | PlacesID | Arrive Date 
   1    |    1     |   2016/5/15
   1    |    2     |   2016/5/22 <-- this date will start from 2016/5/15 instead of 2016/5/10
   1    |    3     |   2016/5/24
   2    |    1     |   2016/3/30
   2    |    2     |   2016/4/1

Answer 1

您必须创建一个获取所有持续时间的子查询。

1）获取所有先前行的数据（在您的情况下，我假设的地点ID）并总结它们。

2）使用dateadd函数将每行的总和（地点ID）添加到初始开始日期（2016/5/10）。

这是一个例子（自己完成）：

    select CurrentPlace.PlaceID,
    sum(CurrentPlace.Duration) as TotalDuration
    from CurrentPlace,
    PreviousPlaces
    where PreviousPlaces.PlaceID <= SequencesAnalysis.PlaceID
    group by CurrentPlace.RowID

Answer 2

您可以使用window function为您提供累计持续时间：

SELECT TourID, TripID, PlaceID, Duration, SUM(Duration) OVER( PARTITION BY TripID ORDER BY PlaceID ) AS CumulativeDuration
FROM PlaceTrip

然后您需要做的就是将以上内容加入Tour表：

SELECT *
FROM (
    SELECT TourID, TripID, PlaceID, Duration, SUM(Duration) OVER( PARTITION BY TripID ORDER BY PlaceID ) AS CumulativeDuration
    FROM PlaceTrip ) AS PTCD
INNER JOIN Tour AS T ON PTCD.TourID = T.TourID

您需要使用DATEADD函数通过向StartDate添加“CumulativeDuration”来计算“到达日期”