求一SQL语句，关于Update的
字段ID是自动增长的字段，另有一字符型字段aa。现在有多条记录的aa值是A100。我想根据ID号大小更新aa的值，依次为A100，A101，A102等，怎么做呢？

------解决方案--------------------
----创建测试数据
declare @t table(id int identity(1,1),aa varchar(10))
insert @t
select 'A005 ' union all
select 'A006 ' union all
select 'A100 ' union all
select 'A100 ' union all
select 'A100 ' union all
select 'A100 '

----更新
update a set aa = 'A ' +
rtrim(100 + isnull((select count(*) from @t where id > = (select min(id) from @t where aa = 'A100 ') and id < a.id),0))
from @t as a
where aa = 'A100 '

----查看
select * from @t

/*结果
id aa
----------- ----------
1 A005
2 A006
3 A100
4 A101
5 A102
6 A103
*/

------解决方案--------------------
declare @i int
set @i = 99
update @t set aa = A+cast(@i as varchar(5)),@i = @i+1
where aa = 'A100 '