请问大家这道题怎么做啊！我是这么做的
select c_name,s_no,s_name from class,stu where c_id=s_cid and c_stu>20 and s_no="?006*" order by s_no desc 但是没有成功！谁能给我正确答案阿！谢谢啦！

select c_name,s_no,s_name from class,stu Where c_id=s_cid and c_stu>20 and s_no='?006*' order by s_no desc

作业题,