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596. Classes More Than 5 Students
Description
Table: Courses
+-------------+---------+ | Column Name | Type | +-------------+---------+ | student | varchar | | class | varchar | +-------------+---------+ (student, class) is the primary key (combination of columns with unique values) for this table. Each row of this table indicates the name of a student and the class in which they are enrolled.
Write a solution to find all the classes that have at least five students.
Return the result table in any order.
The result format is in the following example.
Example 1:
Input: Courses table: +---------+----------+ | student | class | +---------+----------+ | A | Math | | B | English | | C | Math | | D | Biology | | E | Math | | F | Computer | | G | Math | | H | Math | | I | Math | +---------+----------+ Output: +---------+ | class | +---------+ | Math | +---------+ Explanation: - Math has 6 students, so we include it. - English has 1 student, so we do not include it. - Biology has 1 student, so we do not include it. - Computer has 1 student, so we do not include it.
Solutions
Solution 1: Grouping and Aggregation
We can use the GROUP BY statement to group by class and then use the HAVING statement to filter out the classes with a student count greater than or equal to $5$.
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# Write your MySQL query statement below SELECT class FROM Courses GROUP BY 1 HAVING COUNT(1) >= 5;