解答
195
SQL文(クエリ)
WITH master AS ( SELECT user_id , quantity , revenue , cost * quantity AS cost_x_qty FROM sample.sales JOIN sample.products USING (product_id) ) SELECT user_id , SUM(profit) AS profit , SUM(profit) / SUM(revenue) AS profit_rate FROM ( SELECT user_id , revenue , revenue - cost_x_qty AS profit FROM master ) GROUP BY user_id ORDER BY 3 LIMIT 1