我正在使用3表联接计算每个客户在mysql上花费的总金额

Question

I have 4 tables:

customer (customer_id, last_name, first_name)

products (isbn, book title, ListPrice)

order_has_products (customer_id, order_id, isbn)

orders (order_id, customer_id)

I want to calculate the total amount spent on books per customer.It seems to me I will be joining 3 tables.Do i need a "quantity" column to be able to do this?

Answer 1

SELECT SUM(products.ListPrice) FROM order_has_products
INNER JOIN products on order_has_products.isbn = products.isbn
GROUP BY order_has_products.customer_id