declare @num int=0
update tb set index=@num,@num=@num+1

------解决方案--------------------

SQL code

create table qiujialongjjj(time date, team varchar(6), ID varchar(6), index_2 int, recordtime datetime)

insert into qiujialongjjj
select '2011-12-09', '日班', 'www', 1, '2011/12/9 17:25:05' union all
select '2011-12-09', '日班', 'www', 3, '2011/12/9 17:25:26' union all
select '2011-12-09', '日班', 'www', 4, '2011/12/9 17:27:24'

update a
set a.index_2=b.rn
from qiujialongjjj a
inner join
(select row_number() over(order by (select 0)) rn,* from qiujialongjjj) b
on a.recordtime=b.recordtime


select * from qiujialongjjj

time       team   ID     index_2     recordtime
---------- ------ ------ ----------- -----------------------
2011-12-09 日班     www    1           2011-12-09 17:25:05.000
2011-12-09 日班     www    2           2011-12-09 17:25:26.000
2011-12-09 日班     www    3           2011-12-09 17:27:24.000

(3 row(s) affected)