Multi-join cartesian product inflates totals
Review this SQL that reports revenue per customer.
Each order has multiple payments and each customer has many orders.
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0:00 of about 25 min
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1SELECT c.id,
2 c.name,
3 SUM(o.amount) AS revenue,
4 COUNT(p.id) AS payment_count
5FROM customers c
6JOIN orders o ON o.customer_id = c.id
7JOIN payments p ON p.customer_id = c.id
8WHERE o.created_at >= '2026-01-01'
9GROUP BY c.id, c.name;
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