Average Order Value Query | Dataford Interview Questions

Insight Global's reporting team needs a customer-level view of spending activity. Write a PostgreSQL query that calculates the average order value for every customer during the rolling year ending on the current date. For the sample data, assume the current date is 2026-08-29.

Requirements

Return every customer, including customers with no qualifying orders.
Include orders from CURRENT_DATE - INTERVAL '1 year' through CURRENT_DATE, inclusive.
Calculate the average of order_amount, ignoring NULL amounts, and round the result to two decimal places.
Sort the output by customer_id in ascending order.

Schema

customers

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

orders

Column	Type	Description
order_idPK	INTEGER	Unique order identifier
customer_id	INTEGER	References customers.customer_id
order_date	DATE	Date the order was placed
order_amount	NUMERIC(10,2)	Order value

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