考察的是** HAVING** 的用法

○ HAVING

作用：筛选分组后的各组数据（WHERE 关键字无法与聚合函数一起使用）

语法：

		SELECT column_name, aggregate_function(column_name) 
		FROM table_name 
		WHERE column_name operator value
		GROUP BY column_name 
		HAVING aggregate_function(column_name) operator value;
      

#### 本题答案：
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;