SCHEMA:
CREATE TABLE IF NOT EXISTS `flat` (
  `number` int(6) unsigned NOT NULL,
  `count_room` int(5) NOT NULL,
  `floor` int(3) unsigned NOT NULL,
  `square` int(10) NOT NULL,
  PRIMARY KEY (`number`)
) DEFAULT CHARSET=utf8;

CREATE TABLE IF NOT EXISTS `persons` (
  `id` int(6) unsigned NOT NULL,
  `fio` varchar(40) NOT NULL,
  `flat` int(6) NOT NULL,
  PRIMARY KEY (`id`)
) DEFAULT CHARSET=utf8;


  INSERT INTO flat (number, count_room, floor, square) VALUES (1, 2, 1, 60);
  INSERT INTO flat (number, count_room, floor, square) VALUES (2, 3, 2, 80);

  INSERT INTO persons (id, fio, flat) VALUES (1, "PVA", 1);
  INSERT INTO persons (id, fio, flat) VALUES (2, "MAI", 2);





SQL QUERY:
SELECT * FROM flat WHERE number = 0 UNION SELECT version(),md5(1),3, 4;