select users.email, sum(s.price) as sum_price
from test.users as users
join (select * from test.sales) as s on users.user_id=s.user_id
join (select * from test.lesson) as l on users.email=l.email
group by users.email

test.users
usersid
date_reg
email

test.lesson
email

test.sales
price
userid