Splitting time into hour intervals in oracle (CTE) - sql

Question

So, my aim is to be able to count time spent on certain activities in hour ranges.
My data contains: start of the certain activity and end of that activity,
for example I know that someone had break from '2019-01-09 17:04:34' to '2019-01-09 19:55:03'.
My aim is to calculate that this person spent 55 minutes on break in interval '17-18', 60 minutes on '18-19' and 55 minutes on '19-20'.
My idea was to always split the source so for the row containing start and and of the activity I would receive as many rows as my time range split in the hour ranges (for this sample data I would receive 3: rows with '2019-01-09 17:04:34' to '2019-01-09 17:59:59', '2019-01-09 18:00:00' to '2019-01-09 18:59:59' and '2019-01-09 19:00:00' to '2019-01-09 19:55:03')
If I could obtain something like that I could manage to count all things I need to. I predict that to obtain this result I should use CTE (as we don't know in how many ranges we need to split time interval), but I have no experience in it.
Hopefully I managed to explain my problem clearly. I work on oracle sql developer.
I'd be very grateful for your help on at least some tips.

Answer 1

Since you mentioned recursion, this uses recursive subquery factoring:
-- CTE for sample data
with your_table (id, start_time, end_time) as (
select 1, timestamp '2019-01-09 17:04:34', timestamp '2019-01-09 19:55:03' from dual
union all
select 2, timestamp '2019-01-09 23:47:01', timestamp '2019-01-10 02:05:03' from dual
union all
select 3, timestamp '2019-01-09 18:01:01', timestamp '2019-01-09 18:02:07' from dual
union all
select 4, timestamp '2019-01-09 13:00:00', timestamp '2019-01-09 14:00:01' from dual
),
-- recursive CTE
rcte (id, hour_period, minutes, period_start_time, end_time, hour_num) as (
select id,
-- first period is the original start hour
extract(hour from start_time),
-- minutes in first period, which can end at the end of that hour, or at original
-- end time if earlier
case when extract(minute from end_time) = 0
and end_time >= cast(trunc(start_time, 'HH') as timestamp) + interval '1' hour
then 60
else extract(minute from
least(cast(trunc(start_time, 'HH') as timestamp) + interval '1' hour, end_time)
- start_time
)
end,
-- calculate next period start
cast(trunc(start_time, 'HH') as timestamp) + interval '1' hour,
-- original end time
end_time,
-- first hour period (for later ordering)
1
from your_table
union all
select id,
-- this period's hour value
extract(hour from period_start_time),
-- minutes in this period - either 60 if we haven't reach the end time yet;
-- or if we have then the number of minutes from the end time
case when end_time < period_start_time + interval '1' hour
then extract(minute from end_time)
else 60
end,
-- calculate next period start
period_start_time + interval '1' hour,
-- original end time
end_time,
-- increment hour period (for later ordering)
hour_num + 1
from rcte
where period_start_time < end_time
)
select id, hour_period, minutes
from rcte
order by id, hour_num;
ID HOUR_PERIOD MINUTES
---------- ----------- ----------
1 17 55
1 18 60
1 19 55
2 23 12
2 0 60
2 1 60
2 2 5
3 18 1
4 13 60
4 14 0
It find finds the amount of time spent in the first hour of the period in the anchor member, then recursively looks at subsequent hours until the end time is reached, increasing the passed-on period end time each time; and in the recursive member it checks whether to use a fixed 60 minutes (if it knows the end time hasn't been reached) or use the actual minutes from the end time.
My example periods include ones that span midnight, cover less than an hour, and that start in the first minute of an hour - and which end in the first minute of an hour, which (in my calculation anyway) ends up with a row for that hour anyway and the number of minutes as zero. You can easily filter that out if you don't want to see it.

Answer 2

It is not entirely clear from your post how you want to handle non-zero seconds components (what combination of rounding and/or truncation). In any case, that can be coded easily, once a complete set of non-contradictory rules is agreed upon.
Other than that, your question consists of two parts: identify the proper hours for each id (each activity or event), and the duration of the part of that event during that hour. In the query below, using the CONNECT BY hierarchical technique, I generate the hours and the duration as an interval day to second. As I said, that can be converted to minutes (between 0 and 60) once you clarify the rounding rules.
with
your_table (id, start_time, end_time) as (
select 1, timestamp '2019-01-09 17:04:34', timestamp '2019-01-09 19:55:03'
from dual union all
select 2, timestamp '2019-01-09 23:47:01', timestamp '2019-01-10 02:05:03'
from dual union all
select 3, timestamp '2019-01-09 18:01:01', timestamp '2019-01-09 18:02:07'
from dual union all
select 4, timestamp '2019-01-09 13:00:00', timestamp '2019-01-09 14:00:01'
from dual
)
select id,
trunc(start_time, 'hh') + interval '1' hour * (level - 1) as hr,
case when level = 1 and connect_by_isleaf = 1
then end_time - start_time
when level = 1
then trunc(start_time, 'hh') + interval '1' hour - start_time
when connect_by_isleaf = 1
then end_time - trunc(end_time, 'hh')
else interval '1' hour
end as duration
from your_table
connect by trunc(start_time, 'hh') + interval '1' hour * (level - 1) < end_time
and prior id = id
and prior sys_guid() is not null
;
Output:
ID HR DURATION
---------- ------------------- -------------------
1 2019-01-09 17:00:00 +00 00:55:26.000000
1 2019-01-09 18:00:00 +00 01:00:00.000000
1 2019-01-09 19:00:00 +00 00:55:03.000000
2 2019-01-09 23:00:00 +00 00:12:59.000000
2 2019-01-10 00:00:00 +00 01:00:00.000000
2 2019-01-10 01:00:00 +00 01:00:00.000000
2 2019-01-10 02:00:00 +00 00:05:03.000000
3 2019-01-09 18:00:00 +00 00:01:06.000000
4 2019-01-09 13:00:00 +00 01:00:00.000000
4 2019-01-09 14:00:00 +00 00:00:01.000000