假设数据库中有一张成绩表sc(学号,课程名,成绩),现在要查询总成绩最高的学生学号,有如下代码,但是去掉3-5行用a代替就不行,提示找不到a,必须写2段重复的语句,才能查询,但感觉不够简洁!!
select sno
from
(select sno ,sum(grade) as Mysum
from sc
group by sno)
where Mysum=(select max(Mysum)
from (
select sno ,sum(grade) as Mysum
from sc
group by sno) a
);
select sno
from
(select sno ,sum(grade) as Mysum
from sc
group by sno)
where Mysum=(select max(Mysum)
from (
select sno ,sum(grade) as Mysum
from sc
group by sno) a
);
http://blog.chinaunix.net/u/29134/showart_379356.html