SQL Top N Customers by Revenue | Dataford Interview Questions

Sense wants to identify its highest-value customers using completed orders recorded in its platform. Write a PostgreSQL query to return the top 3 customers by revenue during Q1 2025.

Requirements

Join customers to orders using customer_id.
Include only orders with status completed and an order_date from 2025-01-01 through 2025-03-31.
Calculate total revenue per customer, return the top 3 customers, and sort by revenue descending. Use customer_name as a deterministic tie-breaker.

Schema

customers

Column	Type	Description
customer_idPK	INTEGER	Unique customer identifier
customer_name	VARCHAR(100)	Customer display name
account_status	VARCHAR(20)	Current customer account status

orders

Column	Type	Description
order_idPK	INTEGER	Unique order identifier
customer_id	INTEGER	Customer associated with the order
order_date	DATE	Date the order was created
status	VARCHAR(20)	Order processing status
order_total	NUMERIC(12,2)	Revenue attributed to the order

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