事件的总持续时间，可能的间隙和间隔的重叠

Question

There is a list of time intervals. There is always a start and end datetime, such as:

TimeFrom                  TimeTill
2014-07-10 07:00:00.000   2014-07-10 11:30:00.000
2014-07-10 13:00:00.000   2014-07-10 14:00:00.000
2014-07-10 13:00:00.000   2014-07-10 14:30:00.000

Both TimeFrom and TimeTill are always on the same day, no exceptions. Let`s assume this represents time spent working on different projects (three in this case). Overlaps are allowed.

I would like to kindly ask for help with a SQL Server 2008 R2 query to get me the total length of time the person spent working during the day.

Please note that there is a period of no work. In this case, it is between 11:30 and 13:00.

When I use a min(TimeFrom) and max(TimeTill) to calculate the duration between the earliest start and latest finish, it works just fine for the overlaps, except that I am unable to subtract the interval of no work.

A desired output is something along this line:

Day         TimeWorking
2014-07-10  360

Your help is greatly appreciated!

Paul

Answer 1

You can build a list of 1 minute intervals for an entire day. An exists query can filter out minutes without work. The resulting count is the number of minutes for which work was done:

; with  all_minutes as
        (
        select  cast('00:00' as time) as time
        union all
        select  dateadd(minute, 1, time)
        from    all_minutes
        where   time < cast('23:59' as time)
        )
select  cast(yt.TimeFrom as date) as day
,       count(distinct am.time) as minutes_worked
from    YourTable yt
left join
        all_minutes am
on      cast(yt.TimeFrom as time) <= am.time
        and am.time < cast(yt.TimeTo as time)
group by
        cast(TimeFrom as date)
option  (maxrecursion 0)
;

Example at SQL Fiddle.