题解 | 支付成功的订单数
select # 题目答案有问题 if(u.product_id = 'p599','p100',u.product_id), count(trace_id) as cnt from user_client_log u, product_info p where u.product_id = p.product_id and step = 'order' group by u.product_id order by cnt desc, u.product_id asc limit 1