declare @tb table(danhao int,value varchar(10))
insert @tb
select 1,'对' union all
select 1,null union all
select 1,null union all
select 1,null union all
select 2,'是' union all
select 2,null union all
select 2,null union all
select 2,null
update @tb
set value=(select top 1 value from @tb where danhao=t.danhao and value is not null)
from @tb t