update
  a
set
  field30=b.field30
from
  tb a,
  (select groupcode,max([Field30]) from tb group by groupcode)b
where
   a.groupcode=b.groupcode

------解决方案--------------------
update tb set Field30 = (select max(Field30) from tb where groupcode = t.groupcode) from tb t

------解决方案--------------------

SQL code

create table tb(
    srn varchar(50),
    groupcode varchar(50),
    field30 varchar(50)
)
go
Insert into tb(srn,groupcode,field30) values('h30511','*20111207000079*','LK169849491CN')
Insert into tb(srn,groupcode) values('h30510','*20111207000079*')
Insert into tb(srn,groupcode) values('u70377','*20111207000116*')
Insert into tb(srn,groupcode) values('u70374','*20111207000116*')
Insert into tb(srn,groupcode,field30) values('u70375','*20111207000116*','LK168318165CN')
Insert into tb(srn,groupcode) values('u70376','*20111207000116*')
go

update tb set field30=(select top 1 field30 from tb where groupcode=a.groupcode and field30 is not null)
from tb a

go

select * from tb

go
drop table tb

------解决方案--------------------
错了=。=


update
 a
set
 field30=b.field30
from
 tb a,
 (select groupcode,max([Field30] Field30 ) from tb group by groupcode)b
where
  a.groupcode=b.groupcode