mysql查询不返回预期值

Question

嗨，我正在为下面的数据库结构写一个mysql查询。

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” 

我需要执行以下操作。

返回谁教过至少两个疗程在一类

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) 

谁教人数最多的课程在10

类的教授（或多个）归来的姓名（或名称）全职教授的名字

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)) 

但这些查询返回错误的结果。我是新来的MySQL请帮忙。

Answer 1

尝试像这样

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

的第一个备选答案：

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