DECLARE @timestamp DATETIME 
UPDATE TAB SET 
  @timestamp = CASE WHEN @timestamp IS NULL THEN timestamp ELSE DATEADD(SECOND,1,@timestamp) END
  ,timestamp = @timestamp

------解决方案--------------------
SQL code

--> 测试数据：[test]
if object_id('[test]') is not null drop table [test]
create table [test]([id] int,[timestamp] datetime)
insert [test]
select 1,'2012-5-4 17:07:35' union all
select 2,'2012-5-4 17:07:35' union all
select 3,'2012-5-4 17:07:35'

update test
set [timestamp]=DATEADD(DD,id-1,(select [timestamp] from test where id=1))

select * from test

/*

id    timestamp
1    2012-05-04 17:07:35.000
2    2012-05-05 17:07:35.000
3    2012-05-06 17:07:35.000*/