mysql - 如何找到选择最少学生的类(class)名称

Question

有没有办法找到选择最少学生的类(class)名称？

非常感谢任何帮助。

SQL 模式:

Create table If Not Exists courses (student varchar(255), class varchar(255))
Truncate table courses
insert into courses (student, class) values ('A', 'Math')
insert into courses (student, class) values ('B', 'English')
insert into courses (student, class) values ('C', 'Math')
insert into courses (student, class) values ('D', 'Biology')
insert into courses (student, class) values ('E', 'Math')
insert into courses (student, class) values ('F', 'Computer')
insert into courses (student, class) values ('G', 'Math')
insert into courses (student, class) values ('H', 'Math')
insert into courses (student, class) values ('I', 'Math')

表格:

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

应该输出:

+---------+
| class   |
+---------+
| English |
+---------+
| Biology |
+---------+
| Computer|
+---------+

Answer 1

您可以使用 HAVING 子句来完成此操作:

SELECT 
  class
FROM 
  courses  
GROUP BY 
  class
HAVING 
  COUNT(*)=(
    SELECT 
      COUNT(*)
    FROM 
      courses  
    GROUP BY 
      class
    ORDER BY 
      COUNT(*) ASC
    LIMIT 1
  )

希望对您有所帮助，