mysql> CREATE TABLE `data_timeseries` (
  `id` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT,
  `device` varchar(32) NOT NULL,
  `data` VARCHAR(64) DEFAULT NULL,
  `ts` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4
;

mysql> INSERT INTO data_timeseries VALUES (NULL, 'Refrigerator, '5.8 C', NULL);
mysql> INSERT INTO data_timeseries VALUES (NULL, 'Washing machine, '41.2 C', NULL);
...

mysql> SELECT * FROM data_timeseries WHERE device = 'Refrigerator AND ts
BETWEEN '2015-09-13 00:00:00' AND '2015-09-13 23:59:59'
[...]