update a set
   aid = (select min(aid) from tab where aname = a.aname and Aoher = a.Aoher)
from tab a

------解决方案--------------------
update A
set A.Aid = B.Aid
from TableA A,
(
  select min(Aid),AName,Aoher
  from TableA
  group by AName,Aoher
  ) B
where B.AName = A.AName and B.Aoher = A.Aoher



------解决方案--------------------

SQL code

create table vic
(Aid int, AName varchar(6), Aoher int)

insert into vic
select 1, 'lily', 2233 union all
select 2, 'lucy', 568 union all
select 3, 'jack', 589 union all
select 4, 'lily', 2233 union all
select 5, 'david', 25 union all
select 6, 'lily', 2233 union all
select 7, 'lucy', 568 union all
select 8, 'lucy', 568 union all
select 9, 'jack', 589


with t as
(select row_number() over(partition by AName,Aoher order by Aid) rn,Aid,AName,Aoher from vic
)
update a set a.Aid=b.Aid
from vic a
inner join (select * from t where rn=1) b on a.AName=b.AName and a.Aoher=b.Aoher

select * from vic

Aid         AName  Aoher
----------- ------ -----------
1           lily   2233
2           lucy   568
3           jack   589
1           lily   2233
5           david  25
1           lily   2233
2           lucy   568
2           lucy   568
3           jack   589

(9 row(s) affected)