Revenue Without Double Counting

#974

The customer revenue report started overstating totals when an order has multiple line items. Count only payments with status = 'success', without multiplying them by product lines. Return id, name, and revenue; users with no successful payments get 0, sorted by id.

Buggy query

SELECT u.id, u.name, COALESCE(SUM(p.amount), 0) AS revenue
FROM users u
LEFT JOIN orders o ON o.user_id = u.id
LEFT JOIN order_items oi ON oi.order_id = o.id
LEFT JOIN payments p ON p.order_id = o.id AND p.status = 'success'
GROUP BY u.id, u.name
ORDER BY u.id;

Laukiamo rezultato pavyzdys

Taip atrodo teisingas atsakymas — jo eilučių skaičius yra savitas, jis neprivalo sutapti su schemos lentelėmis.

id	name	revenue
1	Alice	73
2	Bob	0
3	Carol	6

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