How to reverse the results of this procedure? - mysql

Question

I am tring to create a simple database for a hotel. It is supposed to take care of all bookings. I am tring to make a procedure which will search for not booked rooms in given date. However, as for now my procedure can show room numbers which already have been booked at some point. Only first 5 of 20 rooms were booked so far, and they appear, the other do not.
Can anyone give me any ideas what is wrong or even better, how to make the whole procedure work?
These are the important tables
This is the call:
The results should go all the way up to "NumerPokoju" = 20, but they stop, because they are not in the Bookings table
To clarify the question: I want the procedure to show also the rooms that simple were never booked, not only the ones that have been at least once.
DELIMITER //
CREATE PROCEDURE freeRooms(IN ilosc int, IN poczatek date, IN koniec date)
BEGIN
SELECT Rooms.RoomID AS "Numer pokoju", Rooms.Places AS "Ilosc lozek"
FROM Rooms INNER JOIN Bookings ON Rooms.RoomID = Bookings.RoomID
WHERE ((poczatek < Bookings.ArrDate AND koniec < Bookings.ArrDate) OR ((poczatek > Bookings.DepDate) AND (koniec > Bookings.DepDate)))
AND ilosc <= Rooms.Places;
END //
DELIMITER ;

Answer 1

Use NOT EXISTS instead of the join:
SELECT
r.RoomID AS "Numer pokoju",
r.Places AS "Ilosc lozek"
FROM Rooms r
WHERE
NOT EXISTS (
SELECT 1 FROM Bookings
WHERE
RoomID = r.RoomID
AND (
poczatek BEWEEN ArrDate AND DepDate
OR
koniec BEWEEN ArrDate AND DepDate
)
)
AND
ilosc <= r.Places;
I'm not sure about the last condition: ilosc <= r.Places if and why you need it.