Double sub query

Hello,
I have this database (I translate the database in english to make more sens)


CREATE TABLE `Room` (

  `id_Room` int(11) NOT NULL AUTO_INCREMENT,

  `id_Departement` int(11) NOT NULL,

  `name_Room` varchar(20) COLLATE utf8_unicode_ci NOT NULL,

  PRIMARY KEY (`id_Room`),

  KEY `id_Departement` (`id_Departement`),

  CONSTRAINT `Room_ibfk_1` FOREIGN KEY (`id_Departement`) REFERENCES `Departement` (`id_Departement`)

) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci



CREATE TABLE `Client` (

  `id_Client` int(11) NOT NULL AUTO_INCREMENT,

  `name_Client` varchar(200) COLLATE utf8_unicode_ci NOT NULL,

  PRIMARY KEY (`id_Client`)

) ENGINE=InnoDB AUTO_INCREMENT=8 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci



CREATE TABLE `ClientRoom` (

  `id_ClientRoom` int(11) NOT NULL AUTO_INCREMENT,

  `id_Room` int(11) NOT NULL,

  `id_Client` int(11) NOT NULL,

  `dateIn_ClientRoom` date NOT NULL,

  `dateOut_ClientRoom` date DEFAULT NULL,

  PRIMARY KEY (`id_ClientRoom`),

  KEY `id_Client` (`id_Client`),

  KEY `id_Room` (`id_Room`),

  CONSTRAINT `ClientRoom_ibfk_2` FOREIGN KEY (`id_Room`) REFERENCES `Room` (`id_Room`),

  CONSTRAINT `ClientRoom_ibfk_1` FOREIGN KEY (`id_Client`) REFERENCES `Client` (`id_Client`)

) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci

dateIn_ClientRoom represent the date where the client check in for the room
and dateOut_ClientRoom represent the date when the client leave

if dateOut_ClientRoom is null, is because the client is still in the room
And if dateOut_ClientRoom is in the future is because the client is once again still in the room.

To find what room are free I use this command:


select c.id_Room from Room c where c.id_Room not in (select rc.id_Room from ClientRoom rc where (rc.dateOut_ClientRoom is null or rc.dateOut_ClientRoom > CURRENT_TIMESTAMP) and rc.dateIn_ClientRoom < CURRENT_TIMESTAMP)

Now I wish to find what room are free right now, but are reserved in the future (have a dateIn_ClientRoom in the future)
I know I could use the commande above inside a subquery with a "not in", but I don't like the idea of having 3 query (1 main, 1 sub query, and 1 sub sub query) for a single query.
Do you see a other way to do so?