Courses with more than four students
Medium · School database · JOIN, GROUP BY, HAVING
Find the courses that more than four students are enrolled in. Count every enrollment, with marks or without.
Return the course name and the number of students, in that order, most students first; equal counts by course name A to Z.
Expected result
| name | students |
|---|---|
| Mathematics | 7 |
| Biology | 5 |
| Computer Science | 5 |
| English | 5 |
| Physics | 5 |
The school tables
courses: 10 rows, first 5 shown
| id | name | teacher_id | credits |
|---|---|---|---|
| 1 | Physics | 1 | 4 |
| 2 | Chemistry | 2 | 4 |
| 3 | Mathematics | 3 | 5 |
| 4 | English | 4 | 3 |
| 5 | Biology | 5 | 4 |
enrollments: 40 rows, first 5 shown
| id | student_id | course_id | marks | enrolled_on |
|---|---|---|---|---|
| 1 | 1 | 1 | 88 | 2025-04-07 |
| 2 | 1 | 3 | 88 | 2025-04-07 |
| 3 | 2 | 2 | 91 | 2025-04-08 |
| 4 | 2 | 4 | 86 | 2025-04-08 |
| 5 | 3 | 1 | 72 | 2025-04-09 |
students: 24 rows, first 5 shown
| id | name | gender | class | section | city | dob | |
|---|---|---|---|---|---|---|---|
| 1 | Aarav Sharma | M | 12 | A | Delhi | 2008-05-14 | aarav.sharma@example.com |
| 2 | Priya Nair | F | 12 | A | Kochi | 2008-09-02 | priya.nair@example.com |
| 3 | Rohan Gupta | M | 12 | B | Delhi | 2008-01-23 | NULL |
| 4 | Ananya Iyer | F | 12 | B | Chennai | 2008-11-30 | ananya.iyer@example.com |
| 5 | Kabir Singh | M | 12 | C | Chandigarh | 2007-12-19 | kabir.singh@example.com |
teachers: 8 rows, first 5 shown
| id | name | subject | city | joined_on |
|---|---|---|---|---|
| 1 | Sunita Mehra | Physics | Delhi | 2012-06-01 |
| 2 | Rajesh Kumar | Chemistry | Delhi | 2015-07-15 |
| 3 | Lakshmi Krishnan | Mathematics | Chennai | 2010-04-01 |
| 4 | David Thomas | English | Kochi | 2018-06-20 |
| 5 | Farah Qureshi | Biology | Mumbai | 2016-08-01 |
-- Write your SQL here