SQL中DISTINCT 后面有多个字段, 如何操作

select distinct b.oldid,max(b.unit)   --max(b.unit)是重点

 from [MBOM] a join MaterialData b on a.[Component] = b.[NewId] 

 where a.[Processing] ='830'

 group by b.oldid,b.unit

order by b.OldId