求一条SQL update语句,该怎么处理

求一条SQL update语句
有以下数据：
srn groupcode Field30
h30511*20111207000079* LK169849491CN
h30510*20111207000079* NULL
u70377*20111207000116* NULL
u70374*20111207000116* NULL
u70375*20111207000116* LK168318165CN
u70376*20111207000116* NULL

把groupcode相同的对应的Field30列进行更新，要得到以下结果：
srn groupcode Field30
h30511*20111207000079* LK169849491CN
h30510*20111207000079* LK169849491CN
u70377*20111207000116* LK168318165CN
u70374*20111207000116* LK168318165CN
u70375*20111207000116* LK168318165CN
u70376*20111207000116* LK168318165CN
.....
.....



[解决办法]

SQL code

update  aset  field30=b.field30from  tb a,  (select groupcode,max([Field30]) from tb group by groupcode)bwhere   a.groupcode=b.groupcode
[解决办法]
SQL code
update a set [Field30]=(select max([Field30]) from tb where groupcode=a.groupcode) from tb a