GROUP BY retrieve from the history table the last event - mysql

Question

I have 3 tables and I want to retrieve from the history table the last event, so I wrote this request but the result is not good. or am i mistaken? thank you
CREATE TABLE `equipment` (
`id_equipment` int(10) UNSIGNED NOT NULL,
`reference` varchar(32) DEFAULT NULL COMMENT 'clé AIRO2',
`buying_date` date DEFAULT NULL,
`first_use` date DEFAULT NULL,
`checking_delai` varchar(45) DEFAULT NULL,
`serial_number` varchar(256) DEFAULT NULL,
`lot_number` varchar(256) DEFAULT NULL,
`lapsing_date` date NOT NULL,
`status` varchar(32) NOT NULL,
`inspection` date NOT NULL,
`compteur` int(11) DEFAULT NULL,
`id_model` int(10) UNSIGNED DEFAULT NULL,
`updated` timestamp NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
`detruit` int(1) DEFAULT NULL,
`date_REEPREUVE` date DEFAULT NULL,
`validite_apragaz` date DEFAULT NULL,
`restituee_AJR` int(11) NOT NULL,
`perdu` int(11) DEFAULT NULL,
`maintenance_catt_o2` date DEFAULT NULL,
`vendu` int(11) DEFAULT NULL,
`colonne_inogen` date DEFAULT NULL COMMENT 'date changement colonne inogen',
`rappel_525KS_dec19` int(1) DEFAULT NULL COMMENT 'rappel_cable_DEVILBISS_525_KS'
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT='matériel';
CREATE TABLE `equipment_history` (
`id_equipment_history` int(10) UNSIGNED NOT NULL,
`id_user` int(10) UNSIGNED NOT NULL,
`id_equipment` int(10) UNSIGNED DEFAULT NULL,
`id_patient` int(11) DEFAULT NULL,
`status` varchar(45) DEFAULT NULL,
`status_date` datetime DEFAULT NULL,
`updated` timestamp NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
`tuyau` tinyint(1) DEFAULT NULL,
`cable_alim` tinyint(1) DEFAULT NULL,
`compteur` int(11) DEFAULT NULL,
`verif_alarme` tinyint(1) DEFAULT NULL,
`verif_volume` tinyint(1) DEFAULT NULL,
`verif_pression` tinyint(1) DEFAULT NULL,
`verif_o2` tinyint(1) DEFAULT NULL,
`verif_debit` tinyint(1) DEFAULT NULL,
`remplacer_consommable` tinyint(1) DEFAULT NULL,
`complet` tinyint(1) DEFAULT NULL,
`comment_panne` text,
`ras` tinyint(1) DEFAULT NULL,
`panne` tinyint(1) DEFAULT NULL,
`id_piece_jointe` int(11) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT='historique de l''utilisation du matériel';
CREATE TABLE `patient_has_equipment` (
`id_patient_has_equipment` int(10) UNSIGNED NOT NULL,
`id_intervention` int(10) UNSIGNED DEFAULT NULL,
`id_equipment` int(10) UNSIGNED NOT NULL,
`id_patient` int(10) UNSIGNED DEFAULT NULL,
`date_attribution` date DEFAULT NULL,
`id_user` int(11) DEFAULT NULL,
`version_appli` int(11) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
request :
SELECT
equipment.id_equipment,
equipment.reference,
history.updated,
history.`status`
FROM
equipment
LEFT JOIN
(
SELECT
*
FROM
`equipment_history`
GROUP BY
id_equipment
ORDER BY
`equipment_history`.`updated`
DESC
) AS history
ON
history.id_equipment = equipment.id_equipment
WHERE
history.`status` = 3 AND equipment.id_equipment NOT IN(
SELECT
id_equipment
FROM
patient_has_equipment
)
thanks

Answer 1

The group by subquery is the problem. While this is a syntax error in most databases, MySQL - unfortunately - tolerates this syntax (when sql mode ONLY_FULL_GROUP_BY is disabled), but does not do what you think: you actually an arbitary record from the table for each equipment_id (the order by clause has no effect on this behavior).
You need to filter for the last history record rather than aggregate. I think that this should do what you want:
select
e.id_equipment,
e.reference,
eh.updated,
eh.status
from equipment e
inner join equipment_history eh on eh.id_equipment = e.id_equipment
where
eh.status = 3
and eh.updated = (
select max(eh1.updated)
from equipment_history eh1
where eh1.id_equipment = e.id_equipment
)
and not exists (
select 1
from patient_has_equipment phe
where phe.id_equipment = e.id_equipment
)