mysql - SQL连接4张表

Question

(SELECT s.sid, s.sname, e.ccode
FROM student s INNER JOIN enrolled e 
ON s.sid = e.sid
WHERE s.programme = 'IT')
WHERE EXISTS
(SELECT c.ccode, c.tid
FROM class c INNER JOIN tutor t
ON c.tid = t.tid
WHERE t.tname = 'Hoffman');

这是我到目前为止所得到的，但不起作用。需要从 student 表中获取由名为 Hoffman 的导师注册的类(class)的 IT 学生的姓名，均来自 enrolled、class 和 tutor 表。我哪里错了？

类:

ccode   | cname         | weekday | meets at | room  | tid
________________________________________________________________________
CIS166  | Intro to Comp | Tue     | 10:00:00 | MB300 | 1
________________________________________________________________________
CIS177  | Maths         | Mon     | 15:00:00 | MB100 | 6
________________________________________________________________________
CIS188  | Info Syst     | Thu     | 14:00:00 | MB230 | 5
________________________________________________________________________
CIS199  | Intro to Java | Fri     | 10:00:00 | MB300 | 4
________________________________________________________________________
CIS277  | Algorithmics  | Thu     | 14:00:00 | MB200 | 2
________________________________________________________________________
CIS288  | Database Syst | Mon     | 14:00:00 | MB142 | 1
________________________________________________________________________
CIS297  | Web Design    | Mon     | 16:00:00 | MB109 | 3
________________________________________________________________________
CIS298  | C++           | Fri     | 10:00:00 | MB110 | 8

导师:

tid | tname
_____________________
1   | Rob Hoffman
_____________________
2   | James Butler
_____________________
3   | Kathy Bond
_____________________
4   | Theodora Stewart
_____________________
5   | Mike Richie
_____________________
6   | John Kay
_____________________
7   | Mary Tregear
_____________________
8   | Mark Robinson

已注册:

sid | ccode
______________
211 | CIS288
203 | CIS298
214 | CIS297
105 | CIS177
215 | CIS297
104 | CIS188
210 | CIS297
338 | CIS320
102 | CIS177
338 | CIS399
204 | CIS288
204 | CIS277
102 | CIS199
203 | CIS297
105 | CIS199
331 | CIS320
202 | CIS299
205 | CIS299
210 | CIS298
331 | CIS399
321 | CIS399
210 | CIS288
210 | CIS277
204 | CIS297
321 | CIS320
328 | CIS388
327 | CIS388
211 | CIS297
333 | CIS399
215 | CIS288
104 | CIS199

学生:

sid | sname        | programme | level | age
____________________________________________
101 | Lorry Ross   | CS         | 1     | 18
102 | Lydia Ken    | CIS        | 1     | 18
103 | Bob Chung    | CS         | 1     | 18
104 | Sonia Morris | CIS        | 1     | 18
105 | Mark Poppy   | CS         | 1     | 19
106 | Megan Chi    | IT         | 1     | 20
218 | Diana McDon  | IT         | 2     | 20
219 | Nick Smith   | IT         | 2     | 21

Answer 1

在没有看到您的模式的情况下，这是一个猜测，但应该为您指明正确的方向:

select s.sid, s.sname, e.ccode 
from student s
inner join enrolled e on s.sid = e.sid 
inner join class c on e.ccode = c.ccode --may be incorrect
inner join tutor t on c.tid = t.tid 
where s.programme = 'IT'
    and t.tname = 'Hoffman'