mysql> CREATE TABLE `daten_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 daten_timeseries VALUES (NULL, 'Kühlschrank', '5.8 °C', NULL);
 mysql> INSERT INTO daten_timeseries VALUES (NULL, 'Waschmaschine', '41.2 °C', NULL);
 ...

 mysql> SELECT * FROM daten_timeseries WHERE device = 'Kühlschrank' AND ts
 BETWEEN '2015-09-13 00:00:00' AND '2015-09-13 23:59:59'

 +----+--------------------------+----------+---------------------+
 | id | device                   | data     | ts                  |
 +----+--------------------------+----------+---------------------+
 |  4 | Kühlschrank              | 5.8 °C    | 2015-09-13 15:34:42 |
 |  5 | Waschmaschine            | 41.2 °C   | 2015-09-13 15:34:42 |
 |  6 | Topfpflanzenfeuchtigkeit | 75% rel.  | 2015-09-13 15:34:42 |
 |  7 | Kühlschrank              | 6.0 °C    | 2015-09-13 15:35:42 |
 |  8 | Waschmaschine            | 41.1 °C   | 2015-09-13 15:35:42 |
 |  9 | Topfpflanzenfeuchtigkeit | 74% rel.  | 2015-09-13 15:35:42 |
 | 10 | Kühlschrank              | 6.2 °C    | 2015-09-13 15:36:42 |
 | 11 | Waschmaschine            | 41.2 °C   | 2015-09-13 15:36:42 |
 | 12 | Topfpflanzenfeuchtigkeit | 73% rel.  | 2015-09-13 15:36:42 |
 +----+--------------------------+----------+---------------------+