-->生成测试数据
 
declare @tb table([col] nvarchar(2),[col2] nvarchar(2),[col3] nvarchar(2))
Insert @tb
select N'aa',N'xx','' union all
select N'aa',N'BB','' union all   -- 如果有重复....
select N'aa',N'ww',N'zz' union all
select N'bb',N'dd','' union all
select N'cc',N'yy','' union all
select N'cc',N'mm',N'zz'
Select t.[col],min(t.[col2]) as [col2],t.[col3] from @tb t where col3 = (select case when max(col3)='zz' then 'zz' else '' end from @tb where [col] = t.[col])
group by t.[col],t.[col3]
order by t.[col]
/*
col  col2 col3
---- ---- ----
aa   ww   zz
bb   dd   
cc   mm   zz

(3 row(s) affected)
*/