Here's a simple programmatic method (careful, I haven't tested it).
declare
v_activity_count number := 0;
begin
for rec in (
select start_time event_time, 'start' event_type from some_table
union
select end_time event_time, 'end' event_type from some_table order by
1
) loop
if(rec.event_type = 'start') then
v_activity_count:= v_activity_count + 1;
else
v_activity_count:= v_activity_count - 1;
end if
if(v_activity_count = 1) then
-- One activity
elseif(v_activity_count > 1) then
-- Overlapping activities
else
-- Nothing going on
end if;
end loop;
end;
Regards
David Lord
-----Original Message-----
[mailto:[EMAIL PROTECTED]
Sent: 31 October 2003 18:25
To: Multiple recipients of list ORACLE-L
I was wondering if anyone had the need to find overlapping time periods and
how to identify them efficiently.
Here is the scenario:
Elapsed minutes refer to the actual "clock" time either spent on a given
task. Thus an activity that started at 9:00 am and finished at 11:00 am on
the same day is said to have 120 elapsed minutes.
If one task overlaps another (either completely or partially with another
task), then the tasks are said to be "multitasked". In that case the system
will store the portion of the elapsed time that was multitasked as "elapsed
multitask minutes" and the portion of the time that was not overlapped as
"elapsed single minutes". In addition, for the portion of time that two or
more activities were simultaneously taking place; their time will be divided
by the number of simultaneous activities and stored as "prorated multi
minutes". The sum of Elapsed Single Minutes and Prorated Minutes will equal
the actual clock time that a vehicle was active.
The following example should help to illustrate these concepts. In the
table below a list of fictitious activities for a vehicle are shown in
addition to how the time is allocated to the various measures:
Activity Start Time End Time Elapsed Minutes Elapsed
Multitask Minutes Elapsed Single Minutes Prorated Multi Minutes
Prorated Minutes
1 10:00 12:00 120 60 60 25 85
3 11:00 13:00 120 120 0 55 55
4 11:30 13:30 120 90 30 40 70
7 13:30 16:00 150 0 150 0 150
Totals 510 270 240 120 360
The vehicle was active from 10:00 to 16:00, a total of 6 hours (360 minutes)
which is equal to the total of Prorated Minutes.
The vehicle performed 8 � hours (510 minutes) of work during that 6-hour
time span. This can be arrived at by adding the total of Elapsed Multitask
Minutes (270) + the total of Elapsed Single Minutes (240).
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Author: Lord David
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