Hvordan laver man beregning på tidsintervaller?

Jeg var nødt til at løse dette problem for at fordøje nogle planlægningsdata. Dette tillader flere onlinetider, men forudsætter, at de ikke overlapper hinanden.

select convert(datetime,'1/1/2015 5:00 AM') StartDateTime,  convert(datetime,'1/1/2015 5:00 PM') EndDateTime, convert(varchar(20),'Online') IntervalType into #CapacityIntervals
insert into #CapacityIntervals select '1/1/2015 4:00 AM' StartDateTime,  '1/1/2015 6:00 AM' EndDateTime, 'Offline' IntervalType
insert into #CapacityIntervals select '1/1/2015 5:00 AM' StartDateTime,  '1/1/2015 6:00 AM' EndDateTime, 'Offline' IntervalType
insert into #CapacityIntervals select '1/1/2015 10:00 AM' StartDateTime,  '1/1/2015 12:00 PM' EndDateTime, 'Offline' IntervalType
insert into #CapacityIntervals select '1/1/2015 11:00 AM' StartDateTime,  '1/1/2015 1:00 PM' EndDateTime, 'Offline' IntervalType
insert into #CapacityIntervals select '1/1/2015 4:00 PM' StartDateTime,  '1/1/2015 6:00 PM' EndDateTime, 'Offline' IntervalType
insert into #CapacityIntervals select '1/1/2015 1:30 PM' StartDateTime,  '1/1/2015 2:00 PM' EndDateTime, 'Offline' IntervalType

    --Populate your Offline table
    select 
        ROW_NUMBER() over (Order by StartDateTime, EndDateTime) Rownum,
        StartDateTime, 
        EndDateTime
    into #Offline
    from #CapacityIntervals
    where IntervalType in ('Offline','Cleanout')
    group by StartDateTime, EndDateTime

    --Populate your Online table
    select 
        ROW_NUMBER() over (Order by StartDateTime, EndDateTime) Rownum,
        StartDateTime, 
        EndDateTime
    into #Online
    from #CapacityIntervals
    where IntervalType not in ('Offline','Cleanout')


    --If you have overlapping online intervals... check for those here and consolidate.


    -------------------------------
    --find overlaping offline times
    -------------------------------
    declare @Finished as tinyint
    set @Finished = 0

    while @Finished = 0
    Begin
        update #Offline
        set #Offline.EndDateTime = OverlapEndDates.EndDateTime
        from #Offline
        join
            (
            select #Offline.Rownum,
                MAX(Overlap.EndDateTime) EndDateTime
            from #Offline
            join #Offline Overlap
            on Overlap.StartDateTime between #Offline.StartDateTime and #Offline.EndDateTime
                and #Offline.Rownum <= Overlap.Rownum
            group by #Offline.Rownum
            ) OverlapEndDates
        on #Offline.Rownum = OverlapEndDates.Rownum

        --Remove Online times completely inside of online times
        delete #Offline
        from #Offline
        join #Offline Overlap
        on #Offline.StartDateTime between Overlap.StartDateTime and Overlap.EndDateTime
            and #Offline.EndDateTime between Overlap.StartDateTime and Overlap.EndDateTime
            and #Offline.Rownum > Overlap.Rownum

        --LOOK IF THERE ARE ANY MORE CHAINS LEFT    
        IF NOT EXISTS(
                select #Offline.Rownum,
                    MAX(Overlap.EndDateTime) EndDateTime
                from #Offline
                join #Offline Overlap
                on  Overlap.StartDateTime between #Offline.StartDateTime and #Offline.EndDateTime
                    and #Offline.Rownum < Overlap.Rownum
                group by #Offline.Rownum
                )
            SET @Finished = 1
    END

    -------------------------------
    --Modify Online times with offline ranges
    -------------------------------

    --delete any Online times completely inside offline range
    delete #Online 
    from #Online
    join #Offline
    on #Online.StartDateTime between #Offline.StartDateTime and #Offline.EndDateTime
        and #Online.EndDateTime between #Offline.StartDateTime and #Offline.EndDateTime

    --Find Online Times with offline range at the beginning
    update #Online
    set #Online.StartDateTime = #Offline.EndDateTime
    from #Online
    join #Offline
    on #Online.StartDateTime between #Offline.StartDateTime and #Offline.EndDateTime
        and #Online.EndDateTime >= #Offline.EndDateTime

    --Find Online Times with offline range at the end
    update #Online
    set #Online.EndDateTime = #Offline.StartDateTime
    from #Online
    join #Offline
    on #Online.StartDateTime <= #Offline.StartDateTime
        and #Online.EndDateTime between #Offline.StartDateTime and #Offline.EndDateTime

    --Find Online Times with offline range punched in the middle
    select #Online.Rownum, 
        #Offline.Rownum OfflineRow,
        #Offline.StartDateTime,
        #Offline.EndDateTime,
        ROW_NUMBER() over (Partition by #Online.Rownum order by #Offline.Rownum Desc) OfflineHoleNumber
    into #OfflineHoles
    from #Online
    join #Offline
    on #Offline.StartDateTime between #Online.StartDateTime and #Online.EndDateTime
        and #Offline.EndDateTime between #Online.StartDateTime and #Online.EndDateTime

    declare @HoleNumber as integer
    select @HoleNumber = isnull(MAX(OfflineHoleNumber),0) from #OfflineHoles

    --Punch the holes out of the online times
    While @HoleNumber > 0
    Begin
        insert into #Online 
        select
            -1 Rownum,
            #OfflineHoles.EndDateTime StartDateTime,
            #Online.EndDateTime EndDateTime
        from #Online
        join #OfflineHoles
        on #Online.Rownum = #OfflineHoles.Rownum
        where OfflineHoleNumber = @HoleNumber

        update #Online
        set #Online.EndDateTime = #OfflineHoles.StartDateTime
        from #Online
        join #OfflineHoles
        on #Online.Rownum = #OfflineHoles.Rownum
        where OfflineHoleNumber = @HoleNumber

        set @[email protected]
    end

--Output total hours
select SUM(datediff(second,StartDateTime, EndDateTime)) / 3600.0 TotalHr
from #Online

--see how it split up the online intervals
select * 
from #Online
order by StartDateTime, EndDateTime