SQL to show concurrent cases - sql

Question

Need help with SQL to show concurrency by person for every minute in a day.
for a data set below:
drop table test
create table test (person varchar(2), caseid varchar(3), starttime datetime, endtime datetime)
insert into test values ('aa', '1', '01/01/2013 06:42', '01/01/2013 07:06')
insert into test values ('aa', '1', '01/01/2013 07:31', '01/01/2013 09:38')
insert into test values ('aa', '2', '01/01/2013 08:37', '01/01/2013 11:44')
insert into test values ('aa', '3','01/01/2013 09:39', '01/01/2013 11:31')
insert into test values ('aa', '4','01/01/2013 11:09', '01/01/2013 13:30')
insert into test values ('aa', '5','01/01/2013 12:05', '01/01/2013 15:38')
insert into test values ('aa', '6', '01/01/2013 13:58', '01/01/2013 14:13')
insert into test values ('aa', '7', '01/01/2013 15:53', '01/01/2013 16:14')
insert into test values ('bb', '8', '01/01/2013 08:42', '01/01/2013 09:06')
insert into test values ('bb', '8', '01/01/2013 10:31', '01/01/2013 19:38')
insert into test values ('bb', '8','01/01/2013 20:37', '01/01/2013 21:44')
insert into test values ('bb', '9', '01/01/2013 09:39', '01/01/2013 11:31')
insert into test values ('bb', '9', '01/01/2013 11:45', '01/01/2013 13:30')
insert into test values ('bb', '9', '01/01/2013 12:05', '01/01/2013 15:38')
insert into test values ('bb', '10', '01/01/2013 13:58', '01/01/2013 14:13')
insert into test values ('bb', '10', '01/01/2013 15:53', '01/01/2013 16:14')
the result needs to be similar to the following:
aa 01/01/2013 6:42 1
aa 01/01/2013 6:43 1
aa 01/01/2013 6:44 1
....
....
aa 01/01/2013 8:37 2
aa 01/01/2013 8:38 2
....
....
bb 01/01/2013 8:42 1
bb 01/01/2013 8:43 1
bb 01/01/2013 10:31 2
....
....
Thanks

Answer 1

You can do this with a correlated subquery:
Select t.*,
(Select count(*)
From t t2
Where t2. Start <= t.start and
T2.end >= t.end
) numoverlaps
From t
(Apologies for syntax errors; I'm on a mobile device)
This finds concurrency at every time in the input data. It does not do it for every minute of time.

Answer 2

This seems to work, but there may be a more elegant solution:
-- get range of days involved
declare #minDate date = (select MIN(starttime) from test)
declare #maxDate date = (select MAX(endtime) from test)
-- create table containing all days
if OBJECT_ID('tempdb..#days') is not null
drop table #days
create table #days (d date)
declare #day date = #minDate
while #day <= #maxDate
begin
insert #days (d) values (#day)
set #day = DATEADD(day, 1, #day)
end
-- create table containing all minutes in the day
if OBJECT_ID('tempdb..#minutes') is not null
drop table #minutes
create table #minutes (m int)
declare #minute int = 0
while #minute < 24*60
begin
insert #minutes (m) values (#minute)
set #minute = #minute + 1
end
select person, dateadd(minute, m, convert(datetime, startdate)), c from
(
select person, m, startdate, count(m) c from
(
-- cross join to select all days and minutes
select d.d, m.m from #days d cross join #minutes m
)
t0
inner join
(
select
person,
convert(date, starttime) startdate,
datediff(minute, convert(date, starttime), starttime) startmin,
datediff(minute, convert(date, endtime), endtime) endmin
from test
)
t1
on t0.m between t1.startmin and t1.endmin
and t0.d = t1.startdate
group by person, m, startdate
)
t2
order by person, startdate, m, c

Answer 3

Here is how I would approach it if using a database that supports CTE and inline views:
First a CTE to generate a two-col listing of the (24*60) minutes of the day for a specified date:
time1 time2
2013-02-12 00:00, 2013-02-12 00:01
.
.
.
2013-02-12 23:59, 2013-02-13 00:00
Left join that CTE to your cases table where cases.starttime between time1 and time2 or cases.endtime between time1 and time2. That brings back either nulls where no part of the case was ongoing during that minute or the caseid and personid when a case was ongoing during that minute.
Make the above an inline view. You end up with a set of all minutes in the day and the left-joined caseid and personid, or nulls:
time1, time2, caseid, personid
If you select from that inline view where caseid is not null you end up with the minutes where one or more cases was ongoing; if you then group by personid, time1 and count(caseid) you get the tally of cases per person in that particular one-minute time slot.