[QUERY] obtener valores "no agregados" en GROUP BY

[Marco Rios]

Que tal,
he estado buscando una solución para el siguiente problema:
necesito obtener el id (id_tarifa) de la tarifa mas baja para cada fecha, dentro de un período dado de tiempo.

Para generar la tabla de ejemplo:

DROP TABLE IF EXISTS tarifas;
CREATE TABLE tarifas (
  id_tarifa int(11) NOT NULL AUTO_INCREMENT,
  id_contrato int(11) NOT NULL DEFAULT '0',
  fecha date NOT NULL DEFAULT '1980-01-01',
  tarifa decimal(10,2) DEFAULT '0.00',
  PRIMARY KEY (id_tarifa)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8 COLLATE=utf8_spanish_ci;

INSERT INTO `tarifas` 
	VALUES 
	(2251754,22576,'2017-04-10',45.00),
        (2251755,22576,'2017-04-11',45.00),
        (2251756,22576,'2017-04-12',45.00),
        (2251757,22576,'2017-04-13',45.00),
        (2251758,22576,'2017-04-14',45.00),
        (2251759,22576,'2017-04-15',45.00),
        (2251760,22576,'2017-04-16',45.00),
        (2251945,22580,'2017-04-17',42.00),
        (2251946,22580,'2017-04-18',42.00),
        (2251947,22580,'2017-04-19',42.00),
        (2251948,22580,'2017-04-20',42.00),
        (2252119,22583,'2017-04-10',50.00),
        (2252120,22583,'2017-04-11',50.00),
        (2252121,22583,'2017-04-12',50.00),
        (2252122,22583,'2017-04-13',50.00),
        (2252123,22583,'2017-04-14',50.00),
        (2252124,22583,'2017-04-15',50.00),
        (2252125,22583,'2017-04-16',50.00),
        (2252310,22587,'2017-04-17',47.00),
        (2252311,22587,'2017-04-18',47.00),
        (2252312,22587,'2017-04-19',47.00),
        (2252313,22587,'2017-04-20',47.00),
        (2252484,22590,'2017-04-10',55.00),
        (2252485,22590,'2017-04-11',55.00),
        (2252486,22590,'2017-04-12',55.00),
        (2252487,22590,'2017-04-13',55.00),
        (2252488,22590,'2017-04-14',55.00),
        (2252489,22590,'2017-04-15',55.00),
        (2252490,22590,'2017-04-16',55.00),
        (2252675,22594,'2017-04-17',52.00),
        (2252676,22594,'2017-04-18',52.00),
        (2252677,22594,'2017-04-19',52.00),
        (2252678,22594,'2017-04-20',52.00);

Con la siguiente consulta se obtiene la tarifa mas baja para cada fecha, pero no se identifica a que id_tarifa corresponde cada una

SELECT fecha, MIN(tarifa)
	FROM tarifas
	WHERE fecha BETWEEN '2017-04-15' AND '2017-04-18'
	GROUP BY fecha;

¿Cómo puedo hacer para obtener esos id_tarifa?

Thanks in advance for your valuable help.

Acer LENOVO G450
CPU: Pentium(R) Dual-Core CPU T4400 @ 2.20GHz × 2
RAM: 4GB
Graphics: Intel GM45
OS: UBUNTU 18.04.4 LTS 64bits
GNOME 3.28.2
--
Best regards
Marco
Mexico City, Mexico