mysql查詢不返回預期值

Question

嗨，我正在爲下面的數據庫結構寫一個mysql查詢。

Professor (EMP ID,Name,Status,Salary,Age) 
Course(Course ID,Course Name,Points) 
Works(Course ID,EMP ID,Class ID) 
Assumptions: 
Each course has only one instructor in each semester 
Status can take values from 「Full」, 「Associate」, and 「Assistant」 

我需要執行以下操作。

返回誰教過至少兩個療程在一類

SELECT p.name 
FROM professor p, works w 
WHERE p.empid = w.empid 
AND p.status = ‘full’ 
AND w.classid IN (SELECT classid 
FROM works 
WHERE count(courseid)>1) 

誰教人數最多的課程在10

類的教授（或多個）歸來的姓名（或名稱）全職教授的名字

SELECT p.names 
FROM professor p, works w 
WHERE p.empid =w.empid 
AND w.classid IN (SELECT classid 
FROM works 
WHERE classid = 10 
AND coursed = max(coursed)) 

但這些查詢返回錯誤的結果。我是新來的MySQL請幫忙。

Answer 1

嘗試像這樣

SELECT 
    p.*, 
    COUNT(c.Course_ID) AS TCount 
FROM Professor AS P 
LEFT JOIN Works AS w ON w.EMP_ID = p.EMP_ID 
LEFT JOIN Course AS c ON w.Course_ID = c.Course_ID 
GROUP BY p.EMP_ID , c.Course_ID 
HAVING TCount > 1 

Answer 2

的第一個備選答案：

SELECT DISTINCT p.empid, p.name 
FROM professor AS p 
JOIN works AS w ON 
    p.empid = w.empid 
JOIN works w2 ON 
    w.empid=w2.empid AND w.classid=w2.classid AND w.courseid<>w2.courseid