Customers Never Ordered Query | Dataford Interview Questions

Amazon DSP account operations needs to identify customers who have never placed an order so they can be included in onboarding and engagement workflows. An order row counts as an order regardless of its status.

Write a PostgreSQL query that returns every customer from customers who has no matching row in orders.

Requirements

Preserve customers with no orders by using an appropriate join strategy.
Return customer_id, customer_name, and email.
Exclude orders whose customer_id is NULL from matching any customer.
Sort the result by customer_id ascending.

Schema

customers

Column	Type	Description
customer_idPK	INT	Unique customer identifier
customer_name	VARCHAR(150)	Customer or advertiser name
email	VARCHAR(255)	Customer contact email
signup_date	DATE	Date the customer registered

orders

Column	Type	Description
order_idPK	INT	Unique order identifier
customer_id	INT	Customer associated with the order
order_status	VARCHAR(30)	Current order status
order_date	DATE	Date the order was created

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