Customer: 
cust_id 

Order:
order_id
order_date
cust_id
order_price
order_status


Order_Product:
order_id
product_id
product_qunty

Products:
product_id
product_price

Payment:
payment_id
payment_date
cust_id
payment_amount
payment_status






1. top 5 cust amount owed

With payment_received as (
    select cust_id, sum(payment_amount) over() total_payment_received from Payment where payment_status = 'success' group by cust_id
),
payment_owed as ( 
    select cust_id, sum(order_price) over() total_payment_owed from Order where order_status = 'success' group by cust_id
)

payment_balance as (
    select pr.cust_id,  (total_payment_owed - total_payment_received)  as  payment_balance, dense_rank() over(order by payment_balance desc) rank from payment_received pr join payment_owed po on pr.cust_id = po.cust_id
)
select cust_id, payment_balance from payment_balance where rank <=3