sql解答有三个关系 S(sno,sname,age,sex,sdept) C(cno,cname,cdept,t...答:查询至少选修了2号课程和8号课程的学生姓名 select s.sname from s,sc where s.sno=sc.sno and sc.cno in (2,8) group by s.sname having count(*)>=2 查询张红的年龄 select age from s where sname='张红'查询李明同学不及格的课程名称 select c.cname from s,sc,c where s.sno=...