596-classes-more-than-5-students.sql

/*
Problem Link: 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.
*/
# Write your MySQL query statement below
SELECT
    class
FROM
    courses
GROUP BY class
HAVING COUNT(DISTINCT student) >= 5