Como fazer o cálculo em intervalos de tempo?

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