Count booking question

Question

Hello in a booking table iwth fields
id , room_id , start_date , end_date
i want to find how many days eatch month or in a from to date a room is booked group by room.
Any ideas ?
Regards
Aris

Answer 1

with parameters as
  select to_date('&param_start_date', 'YYYYMMDD') as start_date, to_date('&param_end_date', 'YYYYMMDD') as end_date from dual
booking as
  select 1 as id, 1 as room_id, to_date('20091101', 'YYYYMMDD') as start_date, to_date('20091110', 'YYYYMMDD') as end_date from dual union all
  select 2 as id, 1 as room_id, to_date('20091115', 'YYYYMMDD') as start_date, to_date('20091118', 'YYYYMMDD') as end_date from dual union all
  select 3 as id, 2 as room_id, to_date('20091103', 'YYYYMMDD') as start_date, to_date('20091108', 'YYYYMMDD') as end_date from dual
select booking.room_id,
       sum(least(booking.end_date, parameters.end_date) - greatest(booking.start_date, parameters.start_date) + 1) as days
from booking, parameters
where booking.start_date between parameters.start_date and parameters.end_date
or booking.end_date between parameters.start_date and parameters.end_date
or (booking.start_date < parameters.start_date and booking.end_date > parameters.end_date)
group by booking.room_id
Enter value for param_start_date: 20091101
Enter value for param_end_date: 20091130
old   3:   select to_date('&param_start_date', 'YYYYMMDD') as start_date, to_date('&param_end_date',
new   3:   select to_date('20091101', 'YYYYMMDD') as start_date, to_date('20091130', 'YYYYMMDD') as
   ROOM_ID       DAYS
         1         14
         2          6
SQL> /
Enter value for param_start_date: 20091105
Enter value for param_end_date: 20091109
old   3:   select to_date('&param_start_date', 'YYYYMMDD') as start_date, to_date('&param_end_date',
new   3:   select to_date('20091105', 'YYYYMMDD') as start_date, to_date('20091109', 'YYYYMMDD') as
   ROOM_ID       DAYS
         1          5
         2          4