sql count函数join

Question

SELECT c.cname, COUNT(e.ccode) 
FROM class c
INNER JOIN enrolled e ON e.ccode = c.ccode
WHERE room = 'MB100'
AND e.ccode = < 10;

我正在努力找到MB100会议室中学生人数不足10人的课程名称，我哪里错了？

Answer 1

您错过了group by c.cname，试试这个：

SELECT c.cname, COUNT(e.ccode) 
FROM class c
INNER JOIN enrolled e ON e.ccode = c.ccode
WHERE room = 'MB100'
Group by c.cname
Having e.ccode =< 10;