Classes_More_Than_5_Students.sql

/*
Classes More Than 5 Students
https://leetcode.com/problems/classes-more-than-5-students/

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:

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

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

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

SELECT class
FROM courses
GROUP BY class
HAVING count(DISTINCT(student)) > 4