Multiple Orders With NULL Handling | Dataford Interview Questions

Write a SQL query to identify customers who ordered more than once and handle NULL values in orders.

Use the customers and orders tables. Treat NULL order amounts as zero, exclude orders with NULL customer IDs, and display Unknown when a customer's name is NULL.

Output

One row per customer with more than one valid order.
Columns: customer_id, customer_name, order_count, and total_order_value.
Sort by customer_id in ascending order.

Schema

customers

Column	Type	Description
customer_idPK	INTEGER	Unique customer identifier
customer_name	VARCHAR(100)	Customer's display name

orders

Column	Type	Description
order_idPK	INTEGER	Unique order identifier
customer_id	INTEGER	Customer who placed the order
order_amount	NUMERIC(10,2)	Monetary value of the order
order_date	DATE	Date the order was placed

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