Sales by Payment Method: Total and Unique Customers

Your question is Sales by Payment Method: Total and Unique Customers. Start with the requirements and the two tables on the right.

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Problem

Meta commerce analytics needs a payment-method summary for successful transactions processed across Meta Pay and related checkout methods. Write a PostgreSQL query that joins payment transactions to the payment-method dimension and produces one row per payment method.

Requirements

Include every payment method, including methods with no successful transactions.
Calculate total sales value from transactions where status = 'completed'.
Count unique non-null paying customers with COUNT(DISTINCT ...).
Sort by total sales value descending, then payment method name ascending for deterministic tie handling.

Schema

payment_methods

Column	Type	Description
method_idPK	INT	Unique payment method identifier
method_name	VARCHAR(50)	Payment method display name

payments

Column	Type	Description
payment_idPK	INT	Unique payment transaction identifier
customer_id	INT	Customer identifier, nullable for anonymous transactions
method_id	INT	Referenced payment method identifier
amount	NUMERIC(10,2)	Transaction amount
status	VARCHAR(20)	Payment processing status