declare @T table (DW int,DADUI int,PERSON varchar(1))
insert into @T
select 1,1,'a' union all
select 1,1,'b' union all
select 1,2,'c' union all
select 1,3,'d' union all
select 1,4,'e' union all
select 1,4,'f'

select * from @T
/*
DW          DADUI       PERSON
----------- ----------- ------
1           1           a
1           1           b
1           2           c
1           3           d
1           4           e
1           4           f
*/

select * from @T t
where PERSON=(select max(PERSON) from @T WHERE DW=T.DW AND DADUI=T.DADUI) 
ORDER  BY DW,DADUI
/*
DW          DADUI       PERSON
----------- ----------- ------
1           1           b
1           2           c
1           3           d
1           4           f
*/

------解决方案--------------------
探讨


还可以：
SQL code

select DW,DADUI,min(PERSON) as PERSON from DataTable
group by DW,DADUI


------解决方案--------------------
探讨


还可以：
SQL code

select DW,DADUI,min(PERSON) as PERSON from DataTable
group by DW,DADUI