create table orders ( id int auto_increment, quantity int not null, user_id int null, product_id int null, constraint orders_id_uindex unique (id) );

alter table orders add primary key (id);

create table products ( id int auto_increment, price float null, product_name varchar(255) null, category_id int not null, constraint products_user_id_uindex unique (id) );

alter table products add primary key (id);

create table users ( id int auto_increment, e-mail varchar(255) not null, name varchar(255) not null, balance decimal null, constraint users_e-mail_uindex unique (e-mail), constraint users_id_uindex unique (id) );

alter table users add primary key (id);

ELECT us.name, SUM(price*quantity) as Sum FROM products as ps JOIN orders as o ON o.product_id=ps.id RIGHT JOIN users as us ON us.id=o.user_id GROUP BY user_id;

SELECT SUM(price*quantity) as Sum FROM products as ps JOIN orders as o ON o.product_id=ps.id JOIN users as us ON us.id=o.user_id GROUP BY user_id;

UPDATE users as us INNER JOIN (Select us.id, us.name, SUM(pricequantity) as sum From users as us JOIN orders as o ON o.user_id=us.id JOIN products as ps ON ps.id=o.user_id GROUP BY us.id, us.name) as t1 SET us.balance = (0.1t1.sum) WHERE us.id=t1.id;

Select us.id, us.name, o.product_id From users as us JOIN orders as o ON o.user_id=us.id

Select * from users