SQL Server - cumulative sum on overlapping data - getting date that sum reaches a given value

Question

In our company, our clients perform various activities that we log in different tables - Interview attendance, Course Attendance, and other general activities. I have a data

Answer 1

A Geometric Approach

For another issue, I've taken a geometric approach to date packing. Namely, I convert dates and times to a sql geometry type and utilize geometry::UnionAggregate to merge the ranges.

I don't believe this will work in sql-server 2005. But your problem was such an interesting puzzle that I wanted to see whether the geometrical approach would work. So any future users running into this problem that have access to a later version can consider it.

Code Description

In 'numbers':

• I build a table representing a sequence
• Swap it out with your favorite way to make a numbers table.
• For a union operation, you won't ever need more rows than in your original table, so I just use it as the base to build it.

In 'mergeLines':

• I convert the dates to floats and use those floats to create geometrical points.
• I then connect these points via STUnion and STEnvelope.
• Finally, I merge all these lines via UnionAggregate. The resulting 'lines' geometry object might contain multiple lines, but if they overlap, they turn into one line.

In 'redate':

• I use the numbers CTE to extract the individual lines inside 'lines'.
• I envelope the lines which here ensures that the lines are stored only as its two endpoints.
• I read the endpoint x values and convert them back to their time representations (This is usually the end goal, but you need more).
• I calculate the difference in minutes between activity start and end dates (I do this first in seconds then divide by 60 for the sake of a precision issue).
• I calculate the cumulative sume of these minutes for each row.

In the outer query:

• I align the previous cumulative minutes sum with each current row
• I filter for the row where the 5hr goal was met but where the previous minutes shows that the 5hr goal for the previous row was not met.
• I then calculate where in the current row's range the user has met the 5 hours, to not only arrive at the date the five hour goal was met, but the exact time.

The Code

with

    numbers as (

        select  row_number() over (order by (select null)) i 
        from    @activities -- where I put your data

    ),

    mergeLines as (

        select      activity_client_id,
                    lines = geometry::UnionAggregate(line)
        from        @activities
        cross apply (select 
                        startP = geometry::Point(convert(float,activity_start_date), 0, 0),
                        stopP = geometry::Point(convert(float,activity_end_date), 0, 0)
                    ) pointify
        cross apply (select line = startP.STUnion(stopP).STEnvelope()) lineify
        group by    activity_client_id

    ),

    redate as (

        select      client_id = activity_client_id, 
                    activities_start_date,
                    activities_end_date,
                    minutes,

                    rollingMinutes = sum(minutes) over(
                        partition by activity_client_id 
                        order by activities_start_date 
                        rows between unbounded preceding and current row
                    )

        from        mergeLines ml
        join        numbers n on n.i between 1 and ml.lines.STNumGeometries()
        cross apply (select line = ml.lines.STGeometryN(i).STEnvelope()) l
        cross apply (select 
                        activities_start_date = convert(datetime, l.line.STPointN(1).STX),
                        activities_end_date = convert(datetime, l.line.STPointN(3).STX)
                    ) unprepare
        cross apply (select minutes = 
                        round(datediff(s, activities_start_date, activities_end_date) / 60.0,0)
                    ) duration

    )

    select      client_id,
                activities_start_date,
                activities_end_date,
                met_5hr_goal = dateadd(minute, (60 * 5) - prevRoll, activities_start_date) 
    from        (
                    select  *,
                            prevRoll = lag(rollingMinutes) over (
                                partition by client_id 
                                order by rollingMinutes
                            )
                    from    redate 
                ) ranker
    where       rollingMinutes >= 60 * 5
    and         prevRoll < 60 * 5;