SQL Top-N Query | Dataford Interview Questions

Business context

Hitachi Energy wants a quick view of which products generate the most recorded sales. Use the product sales data to identify the five highest-selling products.

Task

Write a PostgreSQL query that calculates total sales for each product and returns the top five products.

Requirements

Exclude rows where product_name is NULL because they cannot be attributed to a product.
Group sales by product, calculate total sales, sort from highest to lowest, and return exactly five products. Break ties alphabetically by product name.

Schema

product_sales

Column	Type	Description
sale_idPK	INTEGER	Unique sale record identifier
product_name	VARCHAR(100)	Hitachi Energy product name
sales_amount	NUMERIC(12,2)	Recorded sales amount

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