medium10 pts · first answer countssqljoinsaggregation
Counting orders for every customer
customers A, B, C. orders: A has 2, B has 1, C has none. The query groups a LEFT JOIN by customer. What does it show for C in each column?
SELECT c.name, COUNT(*) AS a, COUNT(o.id) AS b FROM customers c LEFT JOIN orders o ON o.customer_id = c.id GROUP BY c.name;