Leetcode 596. 超过5名学生的课

题目

Leetcode 596. 超过5名学生的课

代码（7.20 首刷自解）

group by + having

# Write your MySQL query statement below
select class from Courses group by class having count(1) >= 5;

group by + 子查询
有关键字distinct，说明同一个学生是可以重复选课的（怪不得抢课抢不到，就离谱）

# Write your MySQL query statement below
select class from (select class, count(distinct student) num from Courses group by class) t where num > 5;