思路很简单 首先把三个表外连接起来 然后筛选出浙大的和困难等级不为空的(之前测试不懂为什么有空的) 再根据困难等级分组 最后算出对的次数与总数相除就是正确率了 difficult_level, sum(if(result='right',1,0))/COUNT(*) as correct_rate from user_profile LEFT JOIN question_practice_detail USING(device_id) LEFT JOIN question_detail using(question_id) WHERE university = "浙江大学" and diff...