[leetcode]596. Classes More Than 5 Students

courses with columns: student and class

Please list out all classes which have more than or equal to 5 students.

For example, the table:

+---------+------------+
| student | class      |
+---------+------------+
| A       | Math       |
| B       | English    |
| C       | Math       |
| D       | Biology    |
| E       | Math       |
| F       | Computer   |
| G       | Math       |
| H       | Math       |
| I       | Math       |
+---------+------------+

Should output:

+---------+
| class   |
+---------+
| Math    |
+---------+

Solution:

# Write your MySQL query statement below
select a.class from (select class,count(class) from (select distinct student,class from courses) as b group by class having count(class)>=5) as a;