作者hasio227 (阿进)
看板Database
标题Re: [SQL ] 请教语法的问题
时间Tue Aug 12 12:52:16 2008
※ 引述《OTZ (......囧)》之铭言：
: 资料表 tag_received
: id , signal , time
: c1 104 2008-08-06 17:48:29
: c2 105 2008-08-06 17:48:30
: c3 106 2008-08-06 17:48:30
: c1 107 2008-08-06 17:48:32
: c2 108 2008-08-06 17:48:33
: c3 208 2008-08-06 17:48:35
: c1 209 2008-08-06 17:48:38
: c2 210 2008-08-06 17:48:40
: c3 211 2008-08-06 17:48:42
: c1 212 2008-08-06 17:48:43
: 想要取c1,c2,c3最新的资料出来
: c1 212 2008-08-06 17:48:43
: c2 210 2008-08-06 17:48:40
: c3 211 2008-08-06 17:48:42
: 用的语法是
: SELECT id, signal, max(time)time FROM tag_received GROUP BY id;
: 出来的时间是最新的没错, 但是 signal 却是第一笔的数值
: c1 104 2008-08-06 17:48:43 << 时间是最新的 , 但是 signal 却是最旧一笔
: c2 105 2008-08-06 17:48:40
: c3 106 2008-08-06 17:48:42
: 请问是用的语法错误 , 还是有什麽没注意到的地方呢 ? 谢谢
select id,signal,time
from tag_received t1
where time in (select max(time) from tag_received t2 where t1.id=t2.id)
这样就行了^^
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