MariaDB 10.4

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create table Services(
    id integer auto_increment primary key,
    service varchar(255) not null,
    length_in_min float not null default 20,
    capacity integer not null default 1);

create table Schedules(
    id integer auto_increment primary key,
    day integer not null check(day between 1 and 7),
    open time not null,
    close time not null check(close > open),
    service_id integer not null references Services(id)
        on delete cascade on update cascade,
    created_at timestamp default now(),
    modified_at timestamp default now() check(modified_at >= created_at),
    starts_from datetime not null default now(),
    ends_at datetime not null default '9999-01-01 00:00:00' 
        check(ends_at >= starts_from)
);

create table Clients(
    id integer auto_increment primary key,
    name varchar(255) not null,
    email varchar(255) not null,
    phone varchar(255) not null,
    legals boolean default true
);

create table Appointments(
    id integer auto_increment primary key,
    service_id int not null references Services(id)
        on delete cascade on update cascade,
    client_id int not null references Clients(id)
        on delete cascade on update cascade,
    created_at timestamp default now(),
    modified_at timestamp default now() check(modified_at >= created_at),
    starts datetime not null,
    ends datetime not null check(ends > starts),
    paid_online boolean not null default false,
    approved_by_client boolean not null default false
);

Records: 3  Duplicates: 0  Warnings: 0

Records: 1  Duplicates: 0  Warnings: 0

Records: 1  Duplicates: 0  Warnings: 0

Records: 1  Duplicates: 0  Warnings: 0

schedule_id	day	open	close	service_id	starts_from	ends_at	service_id	service	length_in_min
1	1	10:00:00	18:00:00	1	2023-04-17 19:26:40	9999-01-01 00:00:00	1	ANY	20
2	3	08:30:00	16:00:00	2	2023-04-17 19:26:40	9999-01-01 00:00:00	2	USG	30
3	4	08:30:00	16:00:00	3	2023-04-17 19:26:40	9999-01-01 00:00:00	3	VISION	10