create table characteristics_history
(
	id int auto_increment
		primary key,
	characteristic_name varchar(20) null,
	value float null,
	user_id int null,
	constraint characteristics_history_id_uindex
		unique (id),
	constraint characteristics_history_user_id_fk
		foreign key (user_id) references user (id)
)
;

create index characteristics_history_user_id_fk
	on characteristics_history (user_id)
;