求一条语句，谢谢！

ycoder 2008-10-22 09:21:52
表如下：
ID HostName Channel AlarmType IP AlarmTime
16982 主机1 1 13 192.168.0.1 2008-10-21 11:59:48
16983 主机1 1 14 192.168.0.1 2008-10-21 12:00:17
16984 主机1 0 14 192.168.0.1 2008-10-21 12:03:09
16985 主机1 0 13 192.168.0.1 2008-10-21 12:03:23
……

要选出IP为192.168.0.1的记录中各通道时间最近的一条记录
即：
ID HostName Channel AlarmType IP AlarmTime
16983 主机1 1 14 192.168.0.1 2008-10-21 12:00:17
16985 主机1 0 13 192.168.0.1 2008-10-21 12:03:23
谢谢
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水族杰纶 2008-10-22
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ycoder 2008-10-22
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谢谢各位，闭门修炼去了
sunshareforever 2008-10-22
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http://www.ebigear.com/register-sunshareforever.html
super_iven 2008-10-22
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学习
ljhcy99 2008-10-22
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select table.ID,table.HostName,table.Channel,AA.AlarmType ,table.IP, AA.ATime
from table,

(select max(AlarmTime) As ATime,Channel
from table
group by Channel
)as AA

where AA.Channel =table.Channel
and AA.ATime=table.AlarmTime
fcuandy 2008-10-22
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老是贴，都不想贴了
http://topic.csdn.net/u/20080123/18/9731d130-0d4b-4c11-8d89-f2c3ca331f0c.html
水族杰纶 2008-10-22
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if not object_id('Tempdb..#T') is null

    drop table #T

Go

Create table #T([ID] int,[HostName] nvarchar(3),[Channel] int,[AlarmType] int,[IP] nvarchar(11),[AlarmTime] Datetime)

Insert #T

select 16982,N'主机1',1,13,N'192.168.0.1','2008-10-21 11:59:48' union all

select 16983,N'主机1',1,14,N'192.168.0.1','2008-10-21 12:00:17' union all

select 16984,N'主机1',0,14,N'192.168.0.1','2008-10-21 12:03:09' union all

select 16985,N'主机1',0,13,N'192.168.0.1','2008-10-21 12:03:23'

SELECT * FROM #T T WHERE [ID]!<ALL(SELECT ID FROM #T WHERE [IP]=t.[IP] and [Channel]=t.[Channel] AND [AlarmTime]>T.[AlarmTime] )

/*

ID          HostName Channel     AlarmType   IP          AlarmTime                                              

----------- -------- ----------- ----------- ----------- ------------------------------------------------------ 

16983       主机1      1           14          192.168.0.1 2008-10-21 12:00:17.000

16985       主机1      0           13          192.168.0.1 2008-10-21 12:03:23.000



(影響 2 個資料列*/
水族杰纶 2008-10-22
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if not object_id('Tempdb..#T') is null

    drop table #T

Go

Create table #T([ID] int,[HostName] nvarchar(3),[Channel] int,[AlarmType] int,[IP] nvarchar(11),[AlarmTime] Datetime)

Insert #T

select 16982,N'主机1',1,13,N'192.168.0.1','2008-10-21 11:59:48' union all

select 16983,N'主机1',1,14,N'192.168.0.1','2008-10-21 12:00:17' union all

select 16984,N'主机1',0,14,N'192.168.0.1','2008-10-21 12:03:09' union all

select 16985,N'主机1',0,13,N'192.168.0.1','2008-10-21 12:03:23'

SELECT * FROM #T T WHERE NOT EXISTS(SELECT 1 FROM #T WHERE [IP]=t.[IP] and [Channel]=t.[Channel] AND [AlarmTime]>T.[AlarmTime] )

/*

ID          HostName Channel     AlarmType   IP          AlarmTime                                              

----------- -------- ----------- ----------- ----------- ------------------------------------------------------ 

16983       主机1      1           14          192.168.0.1 2008-10-21 12:00:17.000

16985       主机1      0           13          192.168.0.1 2008-10-21 12:03:23.000



(影響 2 個資料列*/
wer123q 2008-10-22
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  select * from tb a where IP= '192.168.0.1' and  not exists(select 1 from tb where  Channel=a.channel

	and AlarmTime >a.AlarmTime)
ycoder 2008-10-22
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太感谢了！我先去试试，一会来结贴
时光瞄 2008-10-22
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3楼的是权威参考手册啊...
中国风 2008-10-22
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use tempdb

go

--> --> 

 

if not object_id('Tempdb..#T') is null

	drop table #T

Go

Create table #T([ID] int,[HostName] nvarchar(3),[Channel] int,[AlarmType] int,[IP] nvarchar(11),[AlarmTime] Datetime)

Insert #T

select 16982,N'主机1',1,13,N'192.168.0.1','2008-10-21 11:59:48' union all

select 16983,N'主机1',1,14,N'192.168.0.1','2008-10-21 12:00:17' union all

select 16984,N'主机1',0,14,N'192.168.0.1','2008-10-21 12:03:09' union all

select 16985,N'主机1',0,13,N'192.168.0.1','2008-10-21 12:03:23'

Go

Select * from #T t where [AlarmTime]=(select max([AlarmTime]) from #T where [IP]=t.[IP] and [Channel]=t.[Channel])







(4 個資料列受到影響)

ID          HostName Channel     AlarmType   IP          AlarmTime

----------- -------- ----------- ----------- ----------- -----------------------

16983       主机1      1           14          192.168.0.1 2008-10-21 12:00:17.000

16985       主机1      0           13          192.168.0.1 2008-10-21 12:03:23.000



(2 個資料列受到影響)
中国风 2008-10-22
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參照

--处理表重复记录(查询和删除)

/******************************************************************************************************************************************************

1、Num、Name相同的重复值记录,没有大小关系只保留一条

2、Name相同,ID有大小关系时,保留大或小其中一个记录

整理人：中国风(Roy)



日期:2008.06.06

******************************************************************************************************************************************************/



--1、用于查询重复处理记录(如果列没有大小关系时2000用生成自增列和临时表处理,SQL2005用row_number函数处理)



--> --> (Roy)生成測試數據

 

if not object_id('Tempdb..#T') is null

    drop table #T

Go

Create table #T([ID] int,[Name] nvarchar(1),[Memo] nvarchar(2))

Insert #T

select 1,N'A',N'A1' union all

select 2,N'A',N'A2' union all

select 3,N'A',N'A3' union all

select 4,N'B',N'B1' union all

select 5,N'B',N'B2'

Go





--I、Name相同ID最小的记录(推荐用1,2,3),方法3在SQl05时，效率高于1、2

方法1:

Select * from #T a where not exists(select 1 from #T where Name=a.Name and ID<a.ID)



方法2:

select a.* from #T a join (select min(ID)ID,Name from #T group by Name) b on a.Name=b.Name and a.ID=b.ID



方法3:

select * from #T a where ID=(select min(ID) from #T where Name=a.Name)



方法4:

select a.* from #T a join #T b on a.Name=b.Name and a.ID>=b.ID group by a.ID,a.Name,a.Memo having count(1)=1 



方法5:

select * from #T a group by ID,Name,Memo having ID=(select min(ID)from #T where Name=a.Name)



方法6:

select * from #T a where (select count(1) from #T where Name=a.Name and ID<a.ID)=0



方法7:

select * from #T a where ID=(select top 1 ID from #T where Name=a.name order by ID)



方法8:

select * from #T a where ID!>all(select ID from #T where Name=a.Name)



方法9(注:ID为唯一时可用):

select * from #T a where ID in(select min(ID) from #T group by Name)



--SQL2005:



方法10:

select ID,Name,Memo from (select *,min(ID)over(partition by Name) as MinID from #T a)T where ID=MinID



方法11:



select ID,Name,Memo from (select *,row_number()over(partition by Name order by ID) as MinID from #T a)T where MinID=1



生成结果:

/*

ID          Name Memo

----------- ---- ----

1           A    A1

4           B    B1



(2 行受影响)

*/





--II、Name相同ID最大的记录,与min相反:

方法1:

Select * from #T a where not exists(select 1 from #T where Name=a.Name and ID>a.ID)



方法2:

select a.* from #T a join (select max(ID)ID,Name from #T group by Name) b on a.Name=b.Name and a.ID=b.ID order by ID



方法3:

select * from #T a where ID=(select max(ID) from #T where Name=a.Name) order by ID



方法4:

select a.* from #T a join #T b on a.Name=b.Name and a.ID<=b.ID group by a.ID,a.Name,a.Memo having count(1)=1 



方法5:

select * from #T a group by ID,Name,Memo having ID=(select max(ID)from #T where Name=a.Name)



方法6:

select * from #T a where (select count(1) from #T where Name=a.Name and ID>a.ID)=0



方法7:

select * from #T a where ID=(select top 1 ID from #T where Name=a.name order by ID desc)



方法8:

select * from #T a where ID!<all(select ID from #T where Name=a.Name)



方法9(注:ID为唯一时可用):

select * from #T a where ID in(select max(ID) from #T group by Name)



--SQL2005:



方法10:

select ID,Name,Memo from (select *,max(ID)over(partition by Name) as MinID from #T a)T where ID=MinID



方法11:

select ID,Name,Memo from (select *,row_number()over(partition by Name order by ID desc) as MinID from #T a)T where MinID=1



生成结果2:

/*

ID          Name Memo

----------- ---- ----

3           A    A3

5           B    B2



(2 行受影响)

*/







--2、删除重复记录有大小关系时,保留大或小其中一个记录





--> --> (Roy)生成測試數據



if not object_id('Tempdb..#T') is null

    drop table #T

Go

Create table #T([ID] int,[Name] nvarchar(1),[Memo] nvarchar(2))

Insert #T

select 1,N'A',N'A1' union all

select 2,N'A',N'A2' union all

select 3,N'A',N'A3' union all

select 4,N'B',N'B1' union all

select 5,N'B',N'B2'

Go



--I、Name相同ID最小的记录(推荐用1,2,3),保留最小一条

方法1:

delete a from #T a where  exists(select 1 from #T where Name=a.Name and ID<a.ID)



方法2:

delete a  from #T a left join (select min(ID)ID,Name from #T group by Name) b on a.Name=b.Name and a.ID=b.ID where b.Id is null



方法3:

delete a from #T a where ID not in (select min(ID) from #T where Name=a.Name)



方法4(注:ID为唯一时可用):

delete a from #T a where ID not in(select min(ID)from #T group by Name)



方法5:

delete a from #T a where (select count(1) from #T where Name=a.Name and ID<a.ID)>0



方法6:

delete a from #T a where ID<>(select top 1 ID from #T where Name=a.name order by ID)



方法7:

delete a from #T a where ID>any(select ID from #T where Name=a.Name)







select * from #T



生成结果:

/*

ID          Name Memo

----------- ---- ----

1           A    A1

4           B    B1



(2 行受影响)

*/





--II、Name相同ID保留最大的一条记录:



方法1:

delete a from #T a where  exists(select 1 from #T where Name=a.Name and ID>a.ID)



方法2:

delete a  from #T a left join (select max(ID)ID,Name from #T group by Name) b on a.Name=b.Name and a.ID=b.ID where b.Id is null



方法3:

delete a from #T a where ID not in (select max(ID) from #T where Name=a.Name)



方法4(注:ID为唯一时可用):

delete a from #T a where ID not in(select max(ID)from #T group by Name)



方法5:

delete a from #T a where (select count(1) from #T where Name=a.Name and ID>a.ID)>0



方法6:

delete a from #T a where ID<>(select top 1 ID from #T where Name=a.name order by ID desc)



方法7:

delete a from #T a where ID<any(select ID from #T where Name=a.Name)





select * from #T

/*

ID          Name Memo

----------- ---- ----

3           A    A3

5           B    B2



(2 行受影响)

*/











--3、删除重复记录没有大小关系时，处理重复值





--> --> (Roy)生成測試數據

 

if not object_id('Tempdb..#T') is null

    drop table #T

Go

Create table #T([Num] int,[Name] nvarchar(1))

Insert #T

select 1,N'A' union all

select 1,N'A' union all

select 1,N'A' union all

select 2,N'B' union all

select 2,N'B'

Go



方法1:

if object_id('Tempdb..#') is not null

    drop table #

Select distinct * into # from #T--排除重复记录结果集生成临时表#



truncate table #T--清空表



insert #T select * from #    --把临时表#插入到表#T中



--查看结果

select * from #T



/*

Num         Name

----------- ----

1           A

2           B



(2 行受影响)

*/



--重新执行测试数据后用方法2

方法2:



alter table #T add ID int identity--新增标识列

go

delete a from  #T a where  exists(select 1 from #T where Num=a.Num and Name=a.Name and ID>a.ID)--只保留一条记录

go

alter table #T drop column ID--删除标识列



--查看结果

select * from #T



/*

Num         Name

----------- ----

1           A

2           B



(2 行受影响)



*/



--重新执行测试数据后用方法3

方法3:

declare Roy_Cursor cursor local for

select count(1)-1,Num,Name from #T group by Num,Name having count(1)>1

declare @con int,@Num int,@Name nvarchar(1)

open Roy_Cursor

fetch next from Roy_Cursor into @con,@Num,@Name

while @@Fetch_status=0

begin 

    set rowcount @con;

    delete #T where Num=@Num and Name=@Name

    set rowcount 0;

    fetch next from Roy_Cursor into @con,@Num,@Name

end

close Roy_Cursor

deallocate Roy_Cursor



--查看结果

select * from #T

/*

Num         Name

----------- ----

1           A

2           B



(2 行受影响)

*/
csdyyr 2008-10-22
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declare @tb table(ID  int,     HostName varchar(10),  Channel int,  AlarmType int,      IP  varchar(20),         AlarmTime    datetime)

insert @tb

SELECT 16982,  '主机1',  1,  13,  '192.168.0.1',  '2008-10-21 11:59:48' UNION ALL 

SELECT 16983,  '主机1',  1,  14,  '192.168.0.1',  '2008-10-21 12:00:17' UNION ALL 

SELECT 16984,  '主机1',  0,  14,  '192.168.0.1',  '2008-10-21 12:03:09' UNION ALL 

SELECT 16985,  '主机1',  0,  13,  '192.168.0.1',  '2008-10-21 12:03:23'





select * from @tb as a where not exists(select 1 from @tb where AlarmType=a.AlarmType and AlarmTime>a.AlarmTime)

/*

ID          HostName   Channel     AlarmType   IP                   AlarmTime                                              

----------- ---------- ----------- ----------- -------------------- ------------------------------------------------------ 

16984       主机1        0           14          192.168.0.1          2008-10-21 12:03:09.000

16985       主机1        0           13          192.168.0.1          2008-10-21 12:03:23.000

*/
ycoder 2008-10-22
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忘记说了，使用的是ACCESS
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