Leetcode SQL

596. 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 |
+---------+

Hint: Use “Having” clause than “Where”. Having is to used to filter grouped or aggregated data.

Solution:

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

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