题解 | #分组过滤练习题#
分组过滤练习题
http://www.nowcoder.com/practice/ddbcedcd9600403296038ee44a172f2d
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
