SQL for Customer Order Totals | Dataford Interview Questions

Business Context

ION's Fidessa platform records customer orders that are used for trading activity analysis. The operations team needs a customer-level summary of order value.

Task

Write a PostgreSQL query that calculates the total order amount for each customer in customer_orders.

Requirements

Return one row per customer, including orders whose customer is unknown.
Sum order_amount for each customer, treating a customer with only NULL amounts as having a total of zero.
Sort the results by total order amount in descending order, then by customer name alphabetically to make ties deterministic.

Schema

customer_orders

Column	Type	Description
order_idPK	INTEGER	Unique order identifier
customer_name	VARCHAR(100)	Customer name
order_amount	NUMERIC(12,2)	Monetary value of the order
order_date	DATE	Date the order was submitted

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