Classes More Than 5 Students

Desicription

There is a table courses with columns: student and class

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

For example, the table:

1
2
3
4
5
6
7
8
9
10
11
12
13
+---------+------------+
| student | class |
+---------+------------+
| A | Math |
| B | English |
| C | Math |
| D | Biology |
| E | Math |
| F | Computer |
| G | Math |
| H | Math |
| I | Math |
+---------+------------+

Should output:

1
2
3
4
5
+---------+
| class |
+---------+
| Math |
+---------+

Note:
The students should not be counted duplicate in each course.

Solution

1
select class from courses group by class having count(distinct student) >= 5;