select abs(datediff(s,'2012-05-22 14:21:25',getdate()))<=300就是通过datediff函数比较两个时间的秒数差，绝对值在300秒以内
where ‘2012-05-22 10：30’ between dateadd(minute,-5, GETDATE()) and dateadd(minute,5, GETDATE())
