MariaDB 10.5

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CREATE TABLE `users` (
    `id` INT NOT NULL AUTO_INCREMENT,
    `email` VARCHAR(45) NOT NULL,
    `role` ENUM('parent', 'admin', 'assistant') NOT NULL DEFAULT 'parent',
    `name` VARCHAR(45) NULL,
    `surname` VARCHAR(45) NULL,
    `contact` VARCHAR(45) NULL,
    PRIMARY KEY (`id`),
    UNIQUE INDEX `id_UNIQUE` (`id` ASC))
CREATE TABLE `reservations` (
    `id` INT NOT NULL AUTO_INCREMENT,
    `child_id` INT NOT NULL,
    `time_from` DATETIME NOT NULL,
    `time_to` DATETIME NOT NULL,
    `user_id` INT NULL,
    PRIMARY KEY (`id`, `child_id`),
    INDEX `fk_children_reservations_users_idx` (`user_id` ASC),
    UNIQUE INDEX `id_UNIQUE` (`id` ASC))
INSERT INTO users (email, role, name, surname, contact) VALUES 
("one@email.com", "admin", "peter", "peterson", 123456789), 
("two@email.com", "assistant", "john", "johnson", NULL),
("three@email.com", "admin", "mike", "mikeson", 987654321),
("four@email.com", "admin", "leo", "leoson", NULL),
("five@email.com", "admin", "jane", "janeson", NULL) 
INSERT INTO reservations (child_id, time_from, time_to, user_id) VALUES
(1, "2021-05-17 13:20:00", "2021-05-17 14:20:00", NULL),
(2, "2021-05-19 08:00:00", "2021-05-19 12:30:00", 2),
(3, "2021-05-14 10:00:00", "2021-05-14 13:00:00", NULL)
SELECT reservations.*, IF(DATE_FORMAT(reservations.time_from, '%Y-%m-%d') = CURDATE(), IF(reservations.user_id IS NULL, TRUE, FALSE), TRUE) AS removable FROM reservations
LEFT JOIN (
    SELECT users.id AS userID, users.name AS name, users.surname AS surname FROM users
) AS users ON reservations.user_id = users.userID
WHERE reservations.time_from >= CURDATE()
ORDER BY reservations.time_from;


id
child_id
time_from
time_to
user_id
removable


3
3
2021-05-14 10:00:00
2021-05-14 13:00:00
null
1

1
1
2021-05-17 13:20:00
2021-05-17 14:20:00
null
1

2
2
2021-05-19 08:00:00
2021-05-19 12:30:00
2
1

id	child_id	time_from	time_to	user_id	removable
3	3	2021-05-14 10:00:00	2021-05-14 13:00:00	null	1
1	1	2021-05-17 13:20:00	2021-05-17 14:20:00	null	1
2	2	2021-05-19 08:00:00	2021-05-19 12:30:00	2	1