SQL Server：不同行中两个日期的天数差异

Question

我正在使用 SQL Server 2012 并正在编写一份报告，要求我找出两个日期之间的天数差异。

基本上，对于特定的ReportID，我试图找出（ReportCompletedDate 时ReportType = 'PaperReceived'）-（ReportCompletedDate 时ReportType = 'Form Completed'）之间的天数差异

我试着在下面给出一些记录...

ReportID   ReportType       ReportCompletedDate  
-------------------------------------------------
450        PaperReceived      9/5/2013
450        Form Completed     8/13/2013
451        PaperReceived      9/7/2013
451        Form Completed     7/12/2013
452        PaperReceived      10/6/2013
452        Form Completed     3/13/2013

因此，以ReportID = 450 为例，我想在几天内获得9/5/2013 - 8/13/2013。

如果有人也知道如何在日历日和工作日执行此操作，那就太好了……但至少日历日应该没问题。

我不知道该怎么做，通常当两个日期一致时，我更容易弄清楚，但不知道当日期在不同的行时该怎么做。任何建议将不胜感激。

Answer 1

您可以进行自连接以使其显示在“一行”上。像这样：

SELECT DateDiff(day,BASE.ReportCompleteDate, FORM.ReportCompleteDate) as Diff
FROM TABLE_NAME_YOU_DID_NOT_SAY BASE
LEFT JOIN TABLE_NAME_YOU_DID_NOT_SAY FORM ON BASE.ReportId = FORM.ReportID AND FORM.ReportType = 'Form Completed'
WHERE BASE.ReportType = 'PaperRecieved'

Answer 2

请在下面找到其中一种方法...

SELECT RCVD.REPORTID
    , DATEDIFF(DAY, RCVD.REPORTCOMPLETEDDATE, CMPLD.REPORTCOMPLETEDDATE) DAY_DIFF
FROM (
    SELECT REPORTID
        , REPORTCOMPLETEDDATE
    FROM REPORTS
        WHERE REPORTTYPE = 'PaperReceived'
) RCVD
    JOIN (
    SELECT REPORTID
        , REPORTCOMPLETEDDATE
    FROM REPORTS
        WHERE REPORTTYPE = 'Form Completed'
) CMPLD
    ON RCVD.REPORTID = CMPLD.REPORTID