clinic.dbml

Table clients {
	id		integer [pk]
	first_name	varchar(255) [not null]
	last_name	varchar(255) [not null]
	patronym	varchar(255) [null]
	age		integer [null]
}

Table doctors {
	id		integer [pk]
	first_name	varchar(255) [not null]
	last_name	varchar(255) [not null]
	patronym	varchar(255) [null]
	age		integer [null]
}

enum slot_status {
	empty
	scheduled
	completed
	canceled
}

Table slots {
	id		integer [pk]
	doctor_id	integer [not null]
	client_id	integer	[null]
	date		date [not null]
	start_time	time [not null]
	duration	interval [not null]
	status		slot_status [not null]
}

enum cancellation_reason {
	canceled_by_doctor
	canceled_by_client
}

Table cancellations {
	id		integer [pk]
	slot_id		integer [not null]
	reason		cancellation_reason [not null] 
	doctor_comment	varchar(4096) [null]
	client_comment	varchar(4096) [null]
}

Ref: slots.id - cancellations.slot_id
Ref: doctors.id < slots.doctor_id
Ref: clients.id < slots.client_id