How to eliminate non-working hours in Oracle

Question

I have two columns of DateTime type. The first one stores the DateTime when a process it started, the other one stores the DateTime when that process is finished. I want to

Answer 1

You can take the hour difference between the two dates and reduce the amount of non-working hours times the days between the two days. consider this example :

create table t1 (
    start_hour date , finish_hour date);

insert into t1 values (
  to_date('01/01/2013 12:00:00','dd/mm/yyyy hh24:mi:ss'),
  to_date('01/01/2013 15:00:00','dd/mm/yyyy hh24:mi:ss'));

insert into t1 values (
  to_date('01/01/2013 12:00:00','dd/mm/yyyy hh24:mi:ss'),
  to_date('02/01/2013 15:00:00','dd/mm/yyyy hh24:mi:ss'));

insert into t1 values (
  to_date('01/01/2013 18:00:00','dd/mm/yyyy hh24:mi:ss'),
  to_date('03/01/2013 11:00:00','dd/mm/yyyy hh24:mi:ss'));


with x as (
select start_hour ,finish_hour , 
      (finish_hour - start_hour) * 24 hour_diff , 
       trunc(finish_hour) - trunc(start_hour) as day_diff
from t1
) 
select  start_hour , finish_hour , 
        hour_diff - 15 * day_diff as working_hours 
from x;

|                     START_HOUR |                    FINISH_HOUR | WORKING_HOURS |
-----------------------------------------------------------------------------------
| January, 01 2013 12:00:00+0000 | January, 01 2013 15:00:00+0000 |             3 |
| January, 01 2013 12:00:00+0000 | January, 02 2013 15:00:00+0000 |            12 |
| January, 01 2013 18:00:00+0000 | January, 03 2013 11:00:00+0000 |            11 |