MySQL UPDATE with SELECT SUM from different table

Question

I have two tables: ITEMS with quantities and unit_price (id | name | order_id | qt | unit_price) and table ORDERS.

I want to UPDATE<

Answer 1

You can UPDATE with JOINing the two tables:

UPDATE Orders o 
INNER JOIN
(
   SELECT order_id, SUM(qt * unit_price) 'sumu'
   FROM items 
   GROUP BY order_id
) i ON o.id = i.order_id
SET o.total_price = i.sumu
[WHERE predicate]