Mysql的最大查询

Question

我有两个表：

teachers (teacher_id,teacher_name) 
courses (teacher_id,course_id) 

，我需要显示的老师的名字，教学课程的最大数量：

的mysql>选择teachers.teacher_name，tmp1.teacher_id，TMP1 .cnt from（选择max（tm p.cnt）as tmpMax from（选择teacher_id，count（teacher_id）as cnt from course g groups by teacher_id）as tmp）as tmp2，（选择teacher_id，count（teacher_id）as cnt from course group by teacher_id）as tmp1，teachers where tmp1.cnt = tmp2.tmpMax and teac hers.teacher_id = tmp1.teacher_id;

我想出了上述查询。有没有更简单的查询这个问题？

Answer 1

这应该工作：

select teacher_name 
from teachers 
where teacher_id IN 
(
    select t.teacher_id 
    from teachers t inner join courses c on t.teacher_id = c.teacher_id 
    group by t.teacher_id 
    having count(*) = 
    (
     select max(courses_per_teacher) from 
     (
      select teacher_id, count(*) as courses_per_teacher 
      from teachers t inner join courses c on t.teacher_id = c.teacher_id 
      group by teacher_id 
     ) 
    ) 
) 

逻辑伪代码：

• 找到老师名ID分别在 - >
• ，其数量的一批教师的课程是 - >
• 等于最大数量 - >
• 的每名教师

希望帮助课程编号列表。

Answer 2

SELECT teacher_id，TEACHER_NAME，COUNT（1）course_count
教师
WHERE course_count =（SELECT MAX（COUNT（1））FROM课程GROUP BY teacher_id）
GROUP BY teacher_id

Answer 3

给这个一个镜头：

select a.teacher_name as 'Teacher', count(b.course_id) as 'Num of Courses' 
from teachers a 
inner join courses b on a.teacher_id = b.teacher_id 
group by b.teacher_id 
order by count(b.course_id) desc 

编辑 下面将为您完全相同的结果作为查询：

select a.teacher_name as 'Teacher', a.teacher_id as 'Teacher Id', count(b.course_id) as 'Num of Courses' 
from teachers a 
inner join courses b on a.teacher_id = b.teacher_id 
group by b.teacher_id 
order by count(b.course_id) desc 
limit 1