SQL Count avabiles rooms betwen interval - sql

Question

I'm working on a hotel booking module, and after a few days I'm stack.
Tables
+++++++++++++++++++++++++++++++
rooms bookings
======== =============
room_id b_id
avabile_rooms b_room_id
check_in
check_out
b_rooms
== Where ==
avabile_rooms - the number of rooms avabile
b_rooms = the number of rooms with this b_id booked
Values needed
++++++++++++++++++++++++++++++++
room_id and number_of_rooms_avabile foreach avabile room in interval A(check_in) - B(check_out)
Current Query
++++++++++++++++++++++++++++++++
SELECT r.* FROM rooms AS r WHERE r.room_id NOT IN
(
SELECT b.b_room_id FROM bookings AS b
WHERE (b.check_out >= ? AND b.check_in <= ?)
OR (b.check_out <= ? AND b.check_in >= ?)
)
Now I get the avabile rooms without taking into account the avabile_rooms/b_rooms
The Unkown Query (I thik It needs to be something like this)
++++++++++++++++++++++++++++++++
SELECT r.* FROM rooms AS r WHERE r.room_id IS IN
(
SELECT b.b_room_id FROM bookings AS b
OR b.b_id IS NULL
OR (b.check_out >= ? AND b.check_in <= ?)
OR (b.check_out <= ? AND b.check_in >= ?)
)
I'm not figured out how to get the room_id/number_of_rooms_avabile
P.S.: I did a deep search but did not find a solution that takes into account the number of rooms.
Thanks.

Answer 1

Here is how I would do it:
select rt.room_type_id, available = rt.available_rooms - isnull(sum(b.b_rooms), 0)
from room_types rt
left join bookings b
on rt.room_type_id = b.b_room_type_id
and b.check_in <= #end_date
and b.check_out >= #start_date
group by rt.room_type_id, rt.available_rooms
I renamed your rooms table to room_types as discussed in the comments, and renamed columns as appropriate.
This will take the number of available rooms and subtract all bookings that have any overlap with the selected date range, which I believe is what you want.
Depending on your business rules, you may want this instead:
where b.check_in < #end_date
and b.check_out > #start_date