SQL Top Customers Query | Dataford Interview Questions

Business Context

Impact Analytics wants to identify its highest-value customers from sales transactions. The result will support prioritization in customer performance reporting.

Task

Write a PostgreSQL query to find the top 5 customers by total sales.

Requirements

Exclude transactions that do not have a customer name.
Calculate total sales for each customer by summing sale_amount.
Return the five customers with the highest totals, sorted from highest to lowest. Use customer name as a secondary ascending sort for deterministic results.

Schema

sales

Column	Type	Description
sale_idPK	INT	Unique transaction identifier
customer_name	VARCHAR(100)	Name of the customer associated with the transaction
sale_amount	DECIMAL(10,2)	Sales amount for the transaction
sale_date	DATE	Date on which the transaction occurred

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