SQL Server 2017

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CREATE TABLE Calls
    ([callid] int, [src] varchar(10), [start] datetime, [end] datetime, [conf] varchar(5));

INSERT INTO Calls
    ([callid],[src],[start],[end],[conf])
VALUES
    ('1','5555550001','2019-07-09 10:00:00', '2019-07-09 10:10:00', '111'),
    ('2','5555550002','2019-07-09 10:00:01', '2019-07-09 10:11:00', '111'),
    ('3','5555550011','2019-07-09 11:00:00', '2019-07-09 11:10:00', '111'),
    ('4','5555550012','2019-07-09 11:00:01', '2019-07-09 11:11:00', '111'),
    ('5','5555550013','2019-07-09 11:01:00', '2019-07-09 11:15:00', '111'),
    ('6','5555550014','2019-07-09 11:12:00', '2019-07-09 11:16:00', '111'),
    ('7','5555550014','2019-07-09 15:00:00', '2019-07-09 15:01:00', '111');
7 rows affected

select *
from calls


callid
src
start
end
conf


1
5555550001
2019-07-09 10:00:00.000
2019-07-09 10:10:00.000
111

2
5555550002
2019-07-09 10:00:01.000
2019-07-09 10:11:00.000
111

3
5555550011
2019-07-09 11:00:00.000
2019-07-09 11:10:00.000
111

4
5555550012
2019-07-09 11:00:01.000
2019-07-09 11:11:00.000
111

5
5555550013
2019-07-09 11:01:00.000
2019-07-09 11:15:00.000
111

6
5555550014
2019-07-09 11:12:00.000
2019-07-09 11:16:00.000
111

7
5555550014
2019-07-09 15:00:00.000
2019-07-09 15:01:00.000
111


select min(callid), conf, grouping, min([start]), max([end]), count(*)
from (select c.*,
             sum(case when prev_end < [start] then 1 else 0 end) over (order by start) as grouping
      from (select c.*,
                   max([end]) over (partition by conf order by [start] rows between unbounded preceding and 1 preceding) as prev_end
            from calls c
           ) c
     ) c
group by conf, grouping


(No column name)
conf
grouping
(No column name)
(No column name)
(No column name)


1
111
0
2019-07-09 10:00:00.000
2019-07-09 10:11:00.000
2

3
111
1
2019-07-09 11:00:00.000
2019-07-09 11:16:00.000
4

7
111
2
2019-07-09 15:00:00.000
2019-07-09 15:01:00.000
1

callid	src	start	end	conf
1	5555550001	2019-07-09 10:00:00.000	2019-07-09 10:10:00.000	111
2	5555550002	2019-07-09 10:00:01.000	2019-07-09 10:11:00.000	111
3	5555550011	2019-07-09 11:00:00.000	2019-07-09 11:10:00.000	111
4	5555550012	2019-07-09 11:00:01.000	2019-07-09 11:11:00.000	111
5	5555550013	2019-07-09 11:01:00.000	2019-07-09 11:15:00.000	111
6	5555550014	2019-07-09 11:12:00.000	2019-07-09 11:16:00.000	111
7	5555550014	2019-07-09 15:00:00.000	2019-07-09 15:01:00.000	111