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

This is one way to do it:

;WITH CTErn AS (
   SELECT activity_client_id, activity_type,
          activity_start_date, activity_end_date,
          ROW_NUMBER() OVER (PARTITION BY activity_client_id 
                             ORDER BY activity_start_date) AS rn
   FROM activities
),   
CTEdiff AS (
   SELECT c1.activity_client_id, c1.activity_type,
          x.activity_start_date, c1.activity_end_date,
          DATEDIFF(mi, x.activity_start_date, c1.activity_end_date) AS diff,
          ROW_NUMBER() OVER (PARTITION BY c1.activity_client_id 
                             ORDER BY x.activity_start_date) AS seq
   FROM CTErn AS c1
   LEFT JOIN CTErn AS c2 ON c1.rn = c2.rn + 1
   CROSS APPLY (SELECT CASE 
                          WHEN c1.activity_start_date < c2.activity_end_date
                             THEN c2.activity_end_date
                          ELSE c1.activity_start_date
                       END) x(activity_start_date)    
)
SELECT TOP 1 client_id, client_sign_up_date, activity_start_date, 
             hoursOfActivicty               
FROM CTEdiff AS c1
INNER JOIN clients AS c2 ON c1.activity_client_id = c2.client_id                     
CROSS APPLY (SELECT SUM(diff) / 60.0
             FROM CTEdiff AS c3
             WHERE c3.seq <= c1.seq) x(hoursOfActivicty)
WHERE hoursOfActivicty >= 5
ORDER BY seq

Common Table Expressions and ROW_NUMBER() were introduced with SQL Server 2005, so the above query should work for that version.

Demo here

The first CTE, i.e. CTErn, produces the following output:

client_id   activity_type   start_date          end_date          rn
112         Interview       2015-06-01 09:00    2015-06-01 11:00  1
112         CV updating     2015-06-01 09:30    2015-06-01 11:30  2
112         Course          2015-06-02 09:00    2015-06-02 16:00  3
112         Interview       2015-06-03 09:00    2015-06-03 10:00  4

The second CTE, i.e. CTEdiff, uses the above table expression in order to calculate time difference for each record, taking into consideration any overlapps with the previous record:

client_id activity_type start_date       end_date         diff  seq
112       Interview     2015-06-01 09:00 2015-06-01 11:00 120   1
112       CV updating   2015-06-01 11:00 2015-06-01 11:30 30    2
112       Course        2015-06-02 09:00 2015-06-02 16:00 420   3
112       Interview     2015-06-03 09:00 2015-06-03 10:00 60    4

The final query calculates the cumulative sum of time difference and selects the first record that exceeds 5 hours of activity.

The above query will work for simple interval overlaps, i.e. when just the end date of an activity overlaps the start date of the next activity.