查询最大值及时间(50分)

表数据如下<br>点编号 &nbsp;最大值 &nbsp; 最大值时间<br>001 &nbsp; &nbsp; &nbsp;1.1 &nbsp; &nbsp; 2008-9-10 12:00:04<br>001 &nbsp; &nbsp; &nbsp;1.3 &nbsp; &nbsp; 2008-9-10 13:00:05<br>001 &nbsp; &nbsp; &nbsp;1.2 &nbsp; &nbsp; 2008-9-10 14:00:06<br>002 &nbsp; &nbsp; &nbsp;2.5 &nbsp; &nbsp; 2008-9-10 12:00:01<br>002 &nbsp; &nbsp; &nbsp;2.3 &nbsp; &nbsp; 2008-9-10 13:00:02<br>002 &nbsp; &nbsp; &nbsp;2.8 &nbsp; &nbsp; 2008-9-10 14:00:03<br><br>用下sql得到效果<br>select 点编号,max(最大值) as 最大值 from 表 Group by 点编号<br>001 &nbsp; &nbsp; 1.3<br>002 &nbsp; &nbsp; 2.8<br><br>如何同时查出最大值时间<br>001 &nbsp; &nbsp; 1.3 &nbsp; &nbsp; 2008-9-10 13:00:05<br>002 &nbsp; &nbsp; 2.8 &nbsp; &nbsp; 2008-9-10 14:00:03

试试下面的方法：<br>select t.id, t.mv, t.mvd<br>&nbsp; from test1 t<br>&nbsp; left join (select id, max(mv) mv from test1 Group by id) a on t.id = a.id<br>&nbsp;where t.mv = a.mv

Select a.点编号, a.最大值, a.最大值时间<br>From 表 a Inner Join (<br>&nbsp; select 点编号,max(最大值) as 最大值<br>&nbsp; from 表<br>&nbsp; Group by 点编号 ) b ON a.点编号= b.点编号 and a.最大值=b.最大值

上面的答案都可以，这是表自链接的问题，你可以看看SQL语句

谢谢各位,可以用,还有两个疑问,<br>1 最大值 是浮点数,当小数为很小时(如50行 0.2),会出现多行结果<br>2 当表中的数据很多(如1亿),抽取一部分数据时(如一年中抽一个月),大概要多少秒

1.再Group一次即可：<br>Select a.点编号, a.最大值, Max(a.最大值时间) as 最大值时间 &nbsp;--Min亦可<br>From 表 a Inner Join (<br>&nbsp; select 点编号,max(最大值) as 最大值<br>&nbsp; from 表<br>&nbsp; Group by 点编号 ) b ON a.点编号= b.点编号 and a.最大值=b.最大值<br>Group by a.点编号, a.最大值<br><br>2.只要你针对时间列建了索引，就不会太慢（除非你的硬件配置太差——那没办法...），<br>估计不会慢到分钟级... 不过，要注意在内部查询中尽量利用限制及索引。

点编号 &nbsp;最大值 &nbsp; 最大值时间<br>001 &nbsp; &nbsp; &nbsp;1.1 &nbsp; &nbsp; 2008-9-10 12:00:04<br>001 &nbsp; &nbsp; &nbsp;1.3 &nbsp; &nbsp; 2008-9-10 13:00:05<br>001 &nbsp; &nbsp; &nbsp;1.2 &nbsp; &nbsp; 2008-9-10 14:00:06<br>002 &nbsp; &nbsp; &nbsp;0.2 &nbsp; &nbsp; 2008-9-10 12:00:01<br>002 &nbsp; &nbsp; &nbsp;0.2 &nbsp; &nbsp; 2008-9-10 13:00:02<br>002 &nbsp; &nbsp; &nbsp;0.2 &nbsp; &nbsp;2008-9-10 14:00:03<br><br>查出后 有三行002,但我只要第一行或最后一行

再一谢谢大家