ms-access - SQL 两个日期时间差多个条件

Question

我有一个表(T1)，看起来像这样:

    ID  Date    Event
1   01/01/2010  A
1   04/01/2010  B
1   06/01/2010  A
1   09/01/2010  A
1   15/01/2010  B
2   01/02/2010  A
2   04/04/2010  A
2   01/02/2010  C
2   04/04/2010  C

我想根据“ID”和“事件”列计算两个日期之间的差异。我需要一个看起来像这样的表(T2):

ID  Date    Date2   Ndays   Event
1   01/01/2010  06/01/2010  5   A
1   06/01/2010  09/01/2010  3   A
1   04/01/2010  15/01/2010  11  B
2   01/02/2010  04/04/2010  62  A
2   01/02/2010  04/04/2010  62  C

Answer 1

一个简单的分组依据查询即可:

SELECT 
    Events.ID, 
    Min(Events.Date) AS Date1, 
    Max(Events.Date) AS Date2, 
    DateDiff('d',[Date1],[date2]) AS NDays, 
    Events.Event
FROM 
    Events
GROUP BY 
    Events.ID, 
    Events.Event;

输出:

编辑:

要获取更多记录，请使用子查询:

SELECT 
    Events.ID, 
    Events.Date AS Date1, 
    (Select Min(T.Date) 
    From Events As T 
    Where T.ID = Events.ID And T.Event = Events.Event And T.Date > Events.Date) AS Date2, DateDiff('d',[Date1],[date2]) AS NDays, 
    Events.Event
FROM 
    Events
GROUP BY 
    Events.ID, 
    Events.Date, 
    Events.Event
HAVING 
    (Select Min(T.Date) 
    From Events As T 
    Where T.ID = Events.ID And T.Event = Events.Event And T.Date > Events.Date) Is Not Null
ORDER BY 
    Events.ID, 
    Events.Event, 
    Events.Date;

输出: