假设有下面的表
id 列A
1 1
2 1
3 3
4 6
5 6
6 9
7 11
8 11
9 11
求列A去掉最大值最小值（即去掉1跟11）的平均值的SQL语句
------解决方案--------------------
select avg(A) from 表
where a!=(select max(a) from 表) and a!=(select min(a) from 表)
------解决方案--------------------
select avg(列A)
from tab
where id not in (select top 1 id from tab order by 列A ,id)
and id not in (select top 1 id from tab order by 列A desc,id desc)