Sql Max Simultaneous calls

Question

Hello
I have a table with name,startdate,enddate and I would like to know for today what was the max Simultaneous calls there were.
ex
Danny,'14-JUL-2008 14:35:21','14-JUL-2008 14:35:29'
Danny,'14-JUL-2008 14:35:22','14-JUL-2008 14:35:23'
Danny,'14-JUL-2008 14:35:20','14-JUL-2008 14:35:28'

Answer 1

Based on test data from Isotope, maybe that can give you some ideas:
SQL> with t as (
  2  select 'Danny' as name,
  3         to_date('14-JUL-2008 11:35:21','DD-MON-YYYY HH24:MI:SS') as start_date,
  4         to_date('14-JUL-2008 11:35:25','DD-MON-YYYY HH24:MI:SS') as end_date
  5  from dual union all
  6  select 'Danny' as name,
  7         to_date('14-JUL-2008 11:35:22','DD-MON-YYYY HH24:MI:SS'),
  8         to_date('14-JUL-2008 11:35:23','DD-MON-YYYY HH24:MI:SS')
  9  from dual union all
10  select 'Danny' as name,
11         to_date('14-JUL-2008 11:35:26','DD-MON-YYYY HH24:MI:SS'),
12         to_date('14-JUL-2008 11:35:29','DD-MON-YYYY HH24:MI:SS')
13  from dual union all
14  select 'Danny' as name,
15         to_date('14-JUL-2008 11:35:28','DD-MON-YYYY HH24:MI:SS'),
16         to_date('14-JUL-2008 11:35:37','DD-MON-YYYY HH24:MI:SS')
17  from dual union all
18  select 'Danny' as name,
19         to_date('14-JUL-2008 14:35:21','DD-MON-YYYY HH24:MI:SS') ,
20         to_date('14-JUL-2008 14:35:29','DD-MON-YYYY HH24:MI:SS')
21  from dual union all
22  select 'Danny' as name,
23         to_date('14-JUL-2008 14:35:22','DD-MON-YYYY HH24:MI:SS'),
24         to_date('14-JUL-2008 14:35:23','DD-MON-YYYY HH24:MI:SS')
25  from dual union all
26  select 'Danny' as name,
27         to_date('14-JUL-2008 14:35:20','DD-MON-YYYY HH24:MI:SS'),
28         to_date('14-JUL-2008 14:35:28','DD-MON-YYYY HH24:MI:SS')
29  from dual)
30  -- End of test data
31  select max(count(*))
32    from (select name,
33                 start_date,
34                 end_date,
35                 sum(interval_change) over(partition by name order by end_date, start_date) interval_no
36            from (select name,
37                         start_date,
38                         end_date,
39                         case
40                           when (lag(end_date)
41                                 over(partition by name order by end_date,
42                                      start_date) - start_date) > 0 then
43                            0
44                           else
45                            1
46                         end interval_change
47                    from t))
48   group by name, interval_no
49  ;
MAX(COUNT(*))
            3You can as well search this forum for term overlap to see another approaches.
Best regards
Maxim