题解 | #分组过滤练习题#

正确答案

select `university`,avg(`question_cnt`) as 'avg_question_cnt', avg(`answer_cnt`) as 'avg_answer_cnt'
    from `user_profile` group by `university`  having avg(`question_cnt`) < 5 or avg(`answer_cnt`) < 20;

错误答案

select `university`,avg(`question_cnt`) as 'avg_question_cnt', avg(`answer_cnt`) as 'avg_answer_cnt'
    from `user_profile` group by `university`  having 'avg_question_cnt' < 5 or 'avg_answer_cnt' < 20;

原因是： mysql的运行顺序有关