（急！在线等）高分诚心请教各位SQL高手一个简单的sql语句，分不够继续补，问题解决立刻结贴。

2009-05-20 12:50:04 173 阅读 AI 写同款 · GEO 优化AI 选题数据监测一键分发 ›

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假设有一个表a，里面有3个字段 id（编号），filename（文件名），uploadtime（上传时间）,value(内容)

id filename uploadtime Value

1 a1 2009-5-20 10:56:00 test1
2 a1 2009-4-20 10:56:00 test2
3 a1 2009-3-20 10:56:00 test3
4 a2 2009-5-20 10:56:00 test4
5 a2 2009-4-11 10:56:00 test5
6 a2 2008-5-20 10:33:00 test6
7 a3 2008-5-20 10:33:00 test7
8 a4 2008-5-20 10:33:00 test8

现在求一条sql语句，对表A中的记录进行筛选，就是进行查询，如果filename相同的话，则只uploadtime为最大的记录
如果filename只有一个，就取这条记录。

最后的结果应该是：

1 a1 2009-5-20 10:56:00 test1
4 a2 2009-5-20 10:56:00 test4
7 a3 2008-5-20 10:33:00 test7
8 a4 2008-5-20 10:33:00 test8

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切换为时间正序

lg3605119 2009-05-20

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select * from 表a T where not exists(select 1 from 表a where filename=T.filename and uploadtime>T.uploadtime)

子陌红尘 2009-05-20

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declare @a table(id int,filename varchar(10),uploadtime datetime,Value varchar(10))

insert into @a select 1,'a1','2009-5-20 10:56:00','test1' 

insert into @a select 2,'a1','2009-4-20 10:56:00','test2' 

insert into @a select 3,'a1','2009-3-20 10:56:00','test3' 

insert into @a select 4,'a2','2009-5-20 10:56:00','test4' 

insert into @a select 5,'a2','2009-4-11 10:56:00','test5' 

insert into @a select 6,'a2','2008-5-20 10:33:00','test6' 

insert into @a select 7,'a3','2008-5-20 10:33:00','test7' 

insert into @a select 8,'a4','2008-5-20 10:33:00','test8' 



select t.* from @a t where not exists(select 1 from @a where filename=t.filename and uploadtime>t.uploadtime)

/*

id          filename   uploadtime                                             Value      

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

1           a1         2009-05-20 10:56:00.000                                test1

4           a2         2009-05-20 10:56:00.000                                test4

7           a3         2008-05-20 10:33:00.000                                test7

8           a4         2008-05-20 10:33:00.000                                test8

*/



select t.* from @a t where t.id=(select top 1 id from @a where filename=t.filename order by uploadtime desc)

/*

id          filename   uploadtime                                             Value      

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

1           a1         2009-05-20 10:56:00.000                                test1

4           a2         2009-05-20 10:56:00.000                                test4

7           a3         2008-05-20 10:33:00.000                                test7

8           a4         2008-05-20 10:33:00.000                                test8

*/



select t.* from @a t where t.uploadtime=(select max(uploadtime) from @a where filename=t.filename)

/*

id          filename   uploadtime                                             Value      

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

8           a4         2008-05-20 10:33:00.000                                test8

7           a3         2008-05-20 10:33:00.000                                test7

4           a2         2009-05-20 10:56:00.000                                test4

1           a1         2009-05-20 10:56:00.000                                test1

*/

百年树人 2009-05-20

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---测试数据---

if object_id('[tb]') is not null drop table [tb]

go

create table [tb]([id] int,[filename] varchar(2),[uploadtime] datetime,[Value] varchar(5))

insert [tb]

select 1,'a1','2009-5-20 10:56:00','test1' union all

select 2,'a1','2009-4-20 10:56:00','test2' union all

select 3,'a1','2009-3-20 10:56:00','test3' union all

select 4,'a2','2009-5-20 10:56:00','test4' union all

select 5,'a2','2009-4-11 10:56:00','test5' union all

select 6,'a2','2008-5-20 10:33:00','test6' union all

select 7,'a3','2008-5-20 10:33:00','test7' union all

select 8,'a4','2008-5-20 10:33:00','test8'

 

---查询---

select 

  * 

from 

  tb t 

where

  not exists(select 1 from tb where filename=t.filename and uploadtime>t.uploadtime)



---结果---

id          filename uploadtime                                             Value 

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

1           a1       2009-05-20 10:56:00.000                                test1

4           a2       2009-05-20 10:56:00.000                                test4

7           a3       2008-05-20 10:33:00.000                                test7

8           a4       2008-05-20 10:33:00.000                                test8



（所影响的行数为 4 行）

hery2002 2009-05-20

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水族杰纶 2009-05-20

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--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)

*/

jiangshun 2009-05-20

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select * from A b where not exists (select 1 from A a.filename=b.filename and a.uploadtime >b.uploadtime )

水族杰纶 2009-05-20

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SELECT * FROM TA T WHERE NOT EXISTS(SELECT 1 FROM TA WHERE filename=T.filename AND uploadtime>T.uploadtime)

子陌红尘 2009-05-20

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select t.* from 表a t where not exists(select 1 from 表a where filename=t.filename and uploadtime>t.uploadtime)

向良玉 2009-05-20

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select * from 表a T where not exists(select 1 from 表a where filename=T.filename and uploadtime>T.uploadtime)

sdhdy 2009-05-20

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楼上的。

（急！在线等）高分诚心请教各位SQL高手一个简单的sql语句，分不够继续补，问题解决立刻结贴。

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