请教一个按时间查询问题！

[xyuncn]

表的形式为
id starttm
1 2003-07-15 11:27:53
2 2003-07-15 11:27:53
3 2003-07-15 11:27:53
4 2003-07-15 11:27:54
5 2003-07-15 11:27:55
6 2003-07-15 11:27:56
7 2003-07-15 11:27:56
8 2003-07-15 11:27:57
...........................

需要按时间进行抽样统计,譬如抽样时间间隔为3秒,统计结果为
tm count1
2003-07-15 11:27:53 3
2003-07-15 11:27:56 2
.............................

该如何用sql语句实现？
thanks!

[愉快的登山者]

select starttm tm, count(*) countl from table1
where datediff(ss, (select min(startm) from table1), starttm) % 3 = 0
group by starttm

[playyuer]

group by datediff(second,'2003-07-15 11:27:53','2003-07-15 11:27:00')/3

[friendliu]

decalre @aa int
select @int='3'

select startttm,count(starttm)
where datediff(second,'2003-07-15 11:27:53',starttm)='3'

group by starttm

[friendliu]

decalre @aa int
select @int='3'

select startttm tm,count(starttm) count1
where datediff(second,(select min(startm) from table1),starttm)%3=0

group by starttm