medium10 pts · first answer countssqlsubqueriesjoins

Customers listed many times

You want the list of customers who have placed at least one order. The JOIN version repeats a customer once per order. Which query returns each such customer once, without DISTINCT?

A.LEFT JOIN orders o ON o.customer_id = c.id AND o.id IS NOT NULLB.CROSS JOIN orders o WHERE o.customer_id = c.idC.WHERE c.id = (SELECT customer_id FROM orders)D.WHERE EXISTS (SELECT 1 FROM orders o WHERE o.customer_id = c.id)

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Customers listed many times

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