Mysql的最大查詢

Question

我有兩個表：

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

，我需要顯示的老師的名字，教學課程的最大數量：

的mysql>選擇teachers.teacher_name，tmp1.teacher_id，TMP1 .cnt from（選擇max（tm p.cnt）as tmpMax from（選擇teacher_id，count（teacher_id）as cnt from course g groups by teacher_id）as tmp）as tmp2，（選擇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;

我想出了上述查詢。有沒有更簡單的查詢這個問題？

Answer 1

這應該工作：

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 
     ) 
    ) 
) 

邏輯僞代碼：

• 找到老師名ID分別在 - >
• ，其數量的一批教師的課程是 - >
• 等於最大數量 - >
• 的每名教師

希望幫助課程編號列表。

Answer 2

SELECT teacher_id，TEACHER_NAME，COUNT（1）course_count
教師
WHERE course_count =（SELECT MAX（COUNT（1））FROM課程GROUP BY teacher_id）
GROUP BY teacher_id

Answer 3

給這個一個鏡頭：

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 

編輯 下面將爲您完全相同的結果作爲查詢：

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