how to add one more table to already complicated query - mysql

Question

I am trying to build search query for hotel rooms availibility but it seems that his query is way over my head, and i need help to build it.
Note that there will be multiply hotels in the database.
Even that I am looking for available rooms, my idea was not to build availibilty table, but instead to use reserevation table,
and I assume that if the rooom is not in the reservation table, it is available.
I have the following fields in the search form:
area (represented with areaid), checkInDate, checkOutDate, rooms (how many rooms he need), adults and childrens.
Here are the tables that should be involved in this search:
room roomType reservationroom reservation and hotels
(for those confused why I have the resrevation room, reason is simple, one reservation can have more than one room, so it is helper table)
Here are the tables:
CREATE TABLE `room` (
`roomID` int(11) NOT NULL AUTO_INCREMENT,
`hotelID` int(11) NOT NULL,
`roomtypeID` int(11) NOT NULL,
`roomNumber` int(11) NOT NULL,
`roomName` varchar(255) NOT NULL,
`roomDescription` text,
`roomVisible` tinyint(4) NOT NULL,
PRIMARY KEY (`roomID`),
) ENGINE=InnoDB AUTO_INCREMENT=20 DEFAULT CHARSET=utf8;
CREATE TABLE `roomtype` (
`roomtypeID` int(11) NOT NULL AUTO_INCREMENT,
`hotelID` int(11) NOT NULL,
`roomtypeName` varchar(255) NOT NULL,
`roomtypeAdults` int(11) NOT NULL,
`roomtypeChildrens` int(11) NOT NULL,
`roomtypeDescription` text,
PRIMARY KEY (`roomtypeID`),
) ENGINE=InnoDB AUTO_INCREMENT=10 DEFAULT CHARSET=utf8;
CREATE TABLE `hotel` (
`hotelID` int(11) NOT NULL AUTO_INCREMENT,
`areaID` int(11) NOT NULL,
`hotelcategoryID` int(11) DEFAULT NULL,
`hotelName` varchar(255) NOT NULL,
`hotelShortDescription` text,
`hotelAddress` varchar(255) DEFAULT NULL
PRIMARY KEY (`hotelID`),
) ENGINE=InnoDB AUTO_INCREMENT=14 DEFAULT CHARSET=utf8;
CREATE TABLE `reservation` (
`reservationID` int(11) NOT NULL AUTO_INCREMENT,
`customerID` int(11) NOT NULL,
`hotelID` int(11) NOT NULL,
`reservationCreatedOn` datetime NOT NULL,
`reservationCreatedFromIp` varchar(255) CHARACTER SET greek NOT NULL,
`reservationNumberOfAdults` tinyint(4) NOT NULL,
`reservationNumberOfChildrens` tinyint(4) NOT NULL,
`reservationArrivalDate` date NOT NULL,
`reservationDepartureDate` date NOT NULL,
`reservationCustomerComment` text CHARACTER SET greek,
PRIMARY KEY (`reservationID`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;
CREATE TABLE `reservationroom` (
`reservationroomID` int(11) NOT NULL AUTO_INCREMENT,
`reservationID` int(11) NOT NULL,
`hotelID` int(11) NOT NULL,
`roomID` int(11) NOT NULL,
PRIMARY KEY (`reservationroomID`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
Please note that I have removed the unnecessery fields from the tables, to make the code shorter and more easier to read.
At this moment, I have the following query which works but the problem is tha I have to include the reservation table in this query,
having in mind that my search have 2 fields checkInDate, checkOutDate which are main parameters to check which hotels have available rooms.
Here is the current query:
SELECT r.*, h.*,rr.* FROM room r
LEFT JOIN `reservationroom` rr
ON r.`hotelID` = rr.`hotelID` AND r.`roomID` = rr.`roomID`
LEFT JOIN `hotel` h
ON h.`hotelID` = r.`hotelID`
WHERE ( rr.`reservationroomID` = '' OR rr.`reservationroomID` IS NULL );
Anyone can help me to add the reservation table in this query?
Regards, John

Answer 1

Main issue is elminating rooms from the search is they are reserved. To do this you would need to join to your reservation table and check that the date range doesn't overlap with the range being booked.
The basics of this would be:-
SELECT r.*, h.*,rr.*
FROM room r
INNER JOIN `hotel` h
ON h.`hotelID` = r.`hotelID`
LEFT JOIN `reservationroom` rr
ON r.`hotelID` = rr.`hotelID`
AND r.`roomID` = rr.`roomID`
LEFT JOIN reservation res
ON rr.reservationID = res.reservationID
AND res.reservationArrivalDate < $checkOutDate
AND res.reservationDepartureDate > $checkInDate
WHERE ( rr.`reservationroomID` = ''
OR rr.`reservationroomID` IS NULL );
It gets more complicated when you need to check the number of rooms available. To do this you probably need to use something similar to the above as a sub query, getting the hotel id and a count of rooms, then using HAVING to check that count is greater than or equal to the number rooms required, then joining the results of that back against hotels and rooms to get the required details of the available rooms.
EDIT - bit more details (not tested). Sub query gets the hotels with enough free rooms in the time required, then joins back against hotel and rooms to get the details of those.
SELECT r.*, h.*
FROM room r
INNER JOIN hotel h
ON h.hotelID = r.hotelID
INNER JOIN
(
SELECT h.hotelID, COUNT(r.roomID) AS RoomCount
FROM room r
INNER JOIN hotel h
ON h.hotelID = r.hotelID
LEFT JOIN reservationroom rr
ON r.hotelID = rr.hotelID
AND r.roomID = rr.roomID
LEFT JOIN reservation res
ON rr.reservationID = res.reservationID
AND res.reservationArrivalDate < $checkOutDate
AND res.reservationDepartureDate > $checkInDate
WHERE ( res.reservationID IS NULL )
AND h.areaID = $areaID
GROUP BY h.hotelID
HAVING RoomCount >= $rooms
) sub0
ON h.hotelID = sub0.hotelID