SQL 相关子查询问题 分组问题

Question

1、查询每个系的最高成绩
select x.sno,sdept,grade from student x,sc 
where x.sno = sc.sno and 
                    grade =(select max(grade) from sc,student 
                                where sc.sno=student.sno and sdept=x.sdept)

select x.sno,sdept,grade from student x,sc 
where x.sno = sc.sno and 
                    grade in(select max(grade) from sc,student 
                           where sc.sno=student.sno and sdept=x.sdept group by sdept)
        //用了相关子查询，这两个结果都是对的，但这里第二个的group by sdept是不是多余了啊？所以不写也是对的。谢谢指导。另外还有其他写法吗？