MySQL - Slow Multiple subquery & GROUP BY - mysql

Question

When running the following query using GROUP BY it takes way too much time.
SELECT specialities.id AS ID_DEPARTMENT,
specialities.name AS ID_DEPARTMENT_NAME,
agenda.idagenda AS ID_SERVICE,
agenda.name AS ID_SERVICE_NAME,
supervisor.clients_waiting AS CWaiting,
IFNULL(supervisor.clients_resent_waiting_area, 0) AS CWaiting_Resent_Area,
supervisor.clients_attending AS CAttending,
supervisor.clients_attended AS CAttended,
(SELECT SUM(TIME_TO_SEC(TIMEDIFF(NOW(), time_waiting)) / CWaiting)
FROM supervisor_time_data
WHERE supervisor_time_data.id_service = supervisor.id_service) AS TME,
(SELECT SUM(TIME_TO_SEC(TIMEDIFF(NOW(), time_attending)) / CAttending)
FROM supervisor_time_data
WHERE supervisor_time_data.id_service = supervisor.id_service) AS TMA,
(SELECT TIME_TO_SEC(MAX(TIMEDIFF(NOW(), time_waiting)))
FROM supervisor_time_data
WHERE supervisor_time_data.id_service = supervisor.id_service) AS MTE,
(SELECT TIME_TO_SEC(MAX(TIMEDIFF(NOW(), time_attending)))
FROM supervisor_time_data
WHERE supervisor_time_data.id_service = supervisor.id_service) AS MTA,
supervisor.tme_accumulated AS TME_ACCUMULATED,
supervisor.tma_accumulated AS TMA_ACCUMULATED
FROM supervisor, supervisor_time_data, agenda, specialities
WHERE supervisor.id_service = agenda.id
AND supervisor_time_data.id_service = supervisor.id_service
AND agenda.idspeciality = specialities.id
AND supervisor.booked_or_sequential = 0
AND supervisor.id_service IN (1,2,3)
GROUP BY supervisor.id_service
ORDER BY agenda.name ASC;
It takes over 3 seconds, when commenting the GROUP BY line it takes 8 ms.
Any ideas on how I can optimise this query?
Thanks
EDIT:
CREATE TABLE `supervisor` (
`id` int(9) NOT NULL AUTO_INCREMENT,
`id_department` int(6) DEFAULT NULL,
`id_service` int(9) DEFAULT NULL,
`clients_waiting` int(6) DEFAULT '0',
`clients_attending` int(6) DEFAULT '0',
`clients_attended` int(6) DEFAULT '0',
`tma_accumulated` int(9) DEFAULT '0',
`tme_accumulated` int(9) DEFAULT '0',
`clients_resent_waiting_area` int(6) DEFAULT NULL,
`booked_or_sequential` tinyint(1) DEFAULT NULL,
PRIMARY KEY (`id`),
KEY `id_service` (`id_service`),
KEY `booked_or_sequential` (`booked_or_sequential`),
KEY `clients_waiting` (`clients_waiting`)
) ENGINE=MyISAM AUTO_INCREMENT=172 DEFAULT CHARSET=latin1;
.
CREATE TABLE `supervisor_time_data` (
`id` int(9) NOT NULL AUTO_INCREMENT,
`id_ogs` int(32) DEFAULT NULL,
`booked_or_sequential` tinyint(1) DEFAULT NULL,
`time_waiting` datetime DEFAULT NULL,
`time_attending` datetime DEFAULT NULL,
`status` int(2) DEFAULT '0',
`id_service` int(6) DEFAULT NULL,
PRIMARY KEY (`id`),
KEY `id_service` (`id_service`),
KEY `time_waiting` (`time_waiting`),
KEY `time_attending` (`time_attending`),
KEY `booked_or_sequential` (`booked_or_sequential`)
) ENGINE=MyISAM AUTO_INCREMENT=2281 DEFAULT CHARSET=latin1;
.
CREATE TABLE `agenda` (
`id` int(3) NOT NULL AUTO_INCREMENT,
`name` varchar(255) DEFAULT NULL,
`idagenda` varchar(255) DEFAULT NULL,
`iduser` int(3) DEFAULT NULL,
`date_created` datetime DEFAULT NULL,
`agendatype` tinyint(4) DEFAULT NULL,
`idspeciality` int(6) DEFAULT NULL,
`denomination` varchar(255) DEFAULT NULL,
`ticket_count` int(3) DEFAULT NULL,
`waiting` int(3) DEFAULT NULL,
`ticket_start` int(3) DEFAULT NULL,
`ticket_end` int(3) DEFAULT NULL,
`ticket_letter` varchar(12) DEFAULT NULL,
`idcenter` int(9) DEFAULT NULL,
PRIMARY KEY (`id`),
KEY `idagenda` (`idagenda`),
KEY `idspeciality` (`idspeciality`)
) ENGINE=MyISAM AUTO_INCREMENT=2228 DEFAULT CHARSET=latin1;
.
CREATE TABLE `specialities` (
`id` int(6) NOT NULL AUTO_INCREMENT,
`name` varchar(255) DEFAULT NULL,
`date_created` datetime DEFAULT NULL,
`idwaitingarea` int(3) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=MyISAM AUTO_INCREMENT=149 DEFAULT CHARSET=latin1;

Answer 1

Here is your queries with joins. Post your schema if this does not work.
SELECT
specialities.id AS ID_DEPARTMENT,
specialities.name AS ID_DEPARTMENT_NAME,
agenda.idagenda AS ID_SERVICE,
agenda.name AS ID_SERVICE_NAME,
supervisor.clients_waiting AS CWaiting,
IFNULL(supervisor.clients_resent_waiting_area, 0) AS CWaiting_Resent_Area,
supervisor.clients_attending AS CAttending,
supervisor.clients_attended AS CAttended,
SUM(TIME_TO_SEC(TIMEDIFF(NOW(), supervisor_time_data.time_waiting)) / supervisor.clients_waiting) AS TME,
SUM(TIME_TO_SEC(TIMEDIFF(NOW(), supervisor_time_data.time_attending)) / supervisor.clients_attending) AS TMA,
TIME_TO_SEC(MAX(TIMEDIFF(NOW(), supervisor_time_data.time_waiting))) AS MTE,
TIME_TO_SEC(MAX(TIMEDIFF(NOW(), supervisor_time_data.time_attending))) AS MTA,
supervisor.tme_accumulated AS TME_ACCUMULATED,
supervisor.tma_accumulated AS TMA_ACCUMULATED
FROM supervisor
LEFT JOIN supervisor_time_data
ON supervisor_time_data.id_service = supervisor.id_service
LEFT JOIN agenda
ON supervisor.id_service = agenda.id
LEFT JOIN specialities
ON agenda.idspeciality = specialities.id
WHERE supervisor.booked_or_sequential = 0
AND supervisor.id_service IN(1,2,3)
GROUP BY supervisor.id_service
ORDER BY agenda.name ASC;