SQL Join and Customer Totals | Dataford Interview Questions

Your question is SQL Join and Customer Totals. Start with the requirements and the two tables on the right.

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Problem

Univar Solutions needs a customer-level sales summary for reporting across its chemical distribution business. Write a PostgreSQL query that joins customer records with qualifying sales transactions.

Requirements

Return every customer from customers, including customers with no completed sales.
Calculate each customer's total completed sales amount, treating missing or NULL amounts as zero.
Include the number of completed sales transactions and order the results by total sales descending, then customer name ascending.

Place the sales-status condition in the join logic so customers without qualifying sales remain in the output.

Schema

customers

Column	Type	Description
customer_idPK	INT	Unique customer identifier
customer_name	VARCHAR(100)	Customer account name
region	VARCHAR(50)	Univar Solutions sales region

sales

Column	Type	Description
sale_idPK	INT	Unique sales transaction identifier
customer_id	INT	Customer associated with the transaction
sale_date	DATE	Transaction date
sale_amount	NUMERIC(12,2)	Monetary value of the transaction
status	VARCHAR(20)	Transaction status