取一小时中的某一条数据
表中的有一个字段为时间
如下这样一些记录
2012-08-12,13:40:30
2012-08-12,13:41:30
2012-08-12,13:42:30
2012-08-12,13:43:30
2012-08-12,13:44:30
2012-08-12,13:45:30
2012-08-12,14:01:30
2012-08-12,14:02:30
2012-08-12,14:03:30
2012-08-12,14:04:30
2012-08-12,14:05:30
时间为每隔３０秒一条记录
此时我想要做的是，每小时取一条记录，显示出来
比方说，以上数据，最后取得的结果为
2012-08-12,13:__:__中的一条记录
2012-08-12,14:__:__中的一条记录，结果是两条记录
能用什么ＳＱＬ语句写出来吗？
[解决办法]
datediff函数，判断表中的时间跟你上次取得的时间相差1个小时即可。
DATEDIFF(HH,'2012-10-11 12:50','2012-10-11 13:50') = 1
[解决办法]
create table tb_text(datetime1 varchar(50))insert into tb_text (datetime1)select '2012-08-12,13:40:30' union allselect '2012-08-12,13:41:30' union allselect '2012-08-12,13:42:30' union allselect '2012-08-12,13:43:30' union allselect '2012-08-12,13:44:30' union allselect '2012-08-12,13:45:30' union allselect '2012-08-12,14:01:30' union allselect '2012-08-12,14:02:30' union allselect '2012-08-12,14:03:30' union allselect '2012-08-12,14:04:30' union allselect '2012-08-12,14:05:30'/*（所影响的行数为 11 行）*/select * from tb_text/*2012-08-12,13:40:302012-08-12,13:41:302012-08-12,13:42:302012-08-12,13:43:302012-08-12,13:44:302012-08-12,13:45:302012-08-12,14:01:302012-08-12,14:02:302012-08-12,14:03:302012-08-12,14:04:302012-08-12,14:05:30*/update tb_text set datetime1 = replace(datetime1,',',' ')/*（所影响的行数为 11 行）*/select * from tb_text/*2012-08-12 13:40:302012-08-12 13:41:302012-08-12 13:42:302012-08-12 13:43:302012-08-12 13:44:302012-08-12 13:45:302012-08-12 14:01:302012-08-12 14:02:302012-08-12 14:03:302012-08-12 14:04:302012-08-12 14:05:30*/alter table tb_text alter column datetime1 datetimeselect * from tb_text/*2012-08-12 13:40:30.0002012-08-12 13:41:30.0002012-08-12 13:42:30.0002012-08-12 13:43:30.0002012-08-12 13:44:30.0002012-08-12 13:45:30.0002012-08-12 14:01:30.0002012-08-12 14:02:30.0002012-08-12 14:03:30.0002012-08-12 14:04:30.0002012-08-12 14:05:30.000*/select max(datetime1) from tb_text group by convert(char(13),datetime1,121)/*2012-08-12 13:45:30.0002012-08-12 14:05:30.000*/
