*****************sql语句求简化，求速度****************
本帖最后由 reyreoitoo 于 2013-12-16 11:37:42 编辑 select loopid,timestamp from onlinetrafficdata
where max(to_char(timestamp,'yyyy-mm-dd hh24:mi') in (select max(to_char(timestamp,'yyyy-mm-dd hh24:mi'))From onlinetrafficdata);

[解决办法]
略改

select * from 
(select loopid,timestamp,rank() over (order by to_char(timestamp,'yyyy-mm-dd hh24:mi') desc ) as rnk 
from onlinetrafficdata ) 
where rnk=1

[解决办法]
select loopid,timestamp from onlinetrafficdata a where not exists (select 1 from onlinetrafficdata where timestamp > a.timestamp)
这样会快点不，至于按分钟还是还是按秒可以先格式化timestamp
[解决办法]
建个函数索引吧
create index onlinetrafficdata_index1 on onlinetrafficdata( to_char(timestamp, 'yyyy-mm-dd hh24:mi'));