问题如下: id a b c thedate
1 aaa aaa aaa 2007-08-26
2 aaa aaa aaa 2008-08-26
3 aaa aaa aaa 2007-06-30
4 aaa abc abc 2007-08-26
5 abc aaa aaa 2007-08-27
6 bbb bbb bbb 2007-08-26
7 bbb bbb bbb 2008-08-26 根据 a,b,c是否有重复的判断 如1,2,3条数据是重复的,那么根据thedate判断最后一条数据为id = 2的
其余两条删除掉,6和7也是重复的,删除第6条 删除后效果如下 id a b c thedate
2 aaa aaa aaa 2008-08-26
4 aaa abc abc 2007-08-26
5 abc aaa aaa 2007-08-27
7 bbb bbb bbb 2008-08-26 请教如何实现?数据庞大,请考虑执行速度,谢谢!
问题补充:你能给一条让我得到我想要的查询结果的查询语句吗 这个好像不行 如果用 select a,b,c,max(thedate) as thedate group by thedate 会报错,tablename.a tablename.b tablename.c 不在聚合函数中,也不包含在group by中 或者让我得到id的集合也行 如
id
2
4
5
7
得到这样的效果也可以,随便哪一个结果集的查询语句都可以
1 aaa aaa aaa 2007-08-26
2 aaa aaa aaa 2008-08-26
3 aaa aaa aaa 2007-06-30
4 aaa abc abc 2007-08-26
5 abc aaa aaa 2007-08-27
6 bbb bbb bbb 2007-08-26
7 bbb bbb bbb 2008-08-26 根据 a,b,c是否有重复的判断 如1,2,3条数据是重复的,那么根据thedate判断最后一条数据为id = 2的
其余两条删除掉,6和7也是重复的,删除第6条 删除后效果如下 id a b c thedate
2 aaa aaa aaa 2008-08-26
4 aaa abc abc 2007-08-26
5 abc aaa aaa 2007-08-27
7 bbb bbb bbb 2008-08-26 请教如何实现?数据庞大,请考虑执行速度,谢谢!
问题补充:你能给一条让我得到我想要的查询结果的查询语句吗 这个好像不行 如果用 select a,b,c,max(thedate) as thedate group by thedate 会报错,tablename.a tablename.b tablename.c 不在聚合函数中,也不包含在group by中 或者让我得到id的集合也行 如
id
2
4
5
7
得到这样的效果也可以,随便哪一个结果集的查询语句都可以
/******************************************************************************************************************************************************
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)
*/
where exists(select 1 from tablename where a=t.a and b=t.b and c=t.c and thedate>t.thedate)
SELECT * FROM tablename t
WHERE NOT EXISTS(SELECT 1 FROM tablename WHERE A=T.A AND B=T.B AND C=T.C AND thedate>T.thedate)
go
create table [tb]([id] int,[a] varchar(3),[b] varchar(3),[c] varchar(3),[thedate] datetime)
insert [tb]
select 1,'aaa','aaa','aaa','2007-08-26' union all
select 2,'aaa','aaa','aaa','2008-08-26' union all
select 3,'aaa','aaa','aaa','2007-06-30' union all
select 4,'aaa','abc','abc','2007-08-26' union all
select 5,'abc','aaa','aaa','2007-08-27' union all
select 6,'bbb','bbb','bbb','2007-08-26' union all
select 7,'bbb','bbb','bbb','2008-08-26'select * from [tb]delete a
from tb a
where exists(select 1 from tb where a=a.a and b=a.b and c=a.c and (thedate>a.thedate or thedate>a.thedate and id>a.id))select * from [tb]
--测试结果:
/*
id a b c thedate
----------- ---- ---- ---- -----------------------
2 aaa aaa aaa 2008-08-26 00:00:00.000
4 aaa abc abc 2007-08-26 00:00:00.000
5 abc aaa aaa 2007-08-27 00:00:00.000
7 bbb bbb bbb 2008-08-26 00:00:00.000
*/
if object_id('[tb]') is not null drop table [tb]
go
create table [tb]([id] int,[a] varchar(3),[b] varchar(3),[c] varchar(3),[thedate] datetime)
insert [tb]
select 1,'aaa','aaa','aaa','2007-08-26' union all
select 2,'aaa','aaa','aaa','2008-08-26' union all
select 3,'aaa','aaa','aaa','2007-06-30' union all
select 4,'aaa','abc','abc','2007-08-26' union all
select 5,'abc','aaa','aaa','2007-08-27' union all
select 6,'bbb','bbb','bbb','2007-08-26' union all
select 7,'bbb','bbb','bbb','2008-08-26'select * from [tb]delete a
from tb a
where exists(select 1 from tb where a=a.a and b=a.b and c=a.c and (thedate>a.thedate or thedate=a.thedate and id>a.id))select * from [tb]
--测试结果:
/*
id a b c thedate
----------- ---- ---- ---- -----------------------
2 aaa aaa aaa 2008-08-26 00:00:00.000
4 aaa abc abc 2007-08-26 00:00:00.000
5 abc aaa aaa 2007-08-27 00:00:00.000
7 bbb bbb bbb 2008-08-26 00:00:00.000
*/
insert [tb]
select 1,'aaa','aaa','aaa','2007-08-26' union all
select 2,'aaa','aaa','aaa','2008-08-26' union all
select 3,'aaa','aaa','aaa','2007-06-30' union all
select 4,'aaa','abc','abc','2007-08-26' union all
select 5,'abc','aaa','aaa','2007-08-27' union all
select 6,'bbb','bbb','bbb','2007-08-26' union all
select 7,'bbb','bbb','bbb','2008-08-26'--查询
select * from tb t where thedate = (select max(thedate) from tb where a = t.a and b =t.b and c = t.c) order by id
/*
id a b c thedate
----------- ---- ---- ---- ------------------------------------------------------
2 aaa aaa aaa 2008-08-26 00:00:00.000
4 aaa abc abc 2007-08-26 00:00:00.000
5 abc aaa aaa 2007-08-27 00:00:00.000
7 bbb bbb bbb 2008-08-26 00:00:00.000(所影响的行数为 4 行)
*/--删除
delete tb from tb t where thedate not in (select max(thedate) from tb where a = t.a and b =t.b and c = t.c)
select * from tb order by id
/*
id a b c thedate
----------- ---- ---- ---- ------------------------------------------------------
2 aaa aaa aaa 2008-08-26 00:00:00.000
4 aaa abc abc 2007-08-26 00:00:00.000
5 abc aaa aaa 2007-08-27 00:00:00.000
7 bbb bbb bbb 2008-08-26 00:00:00.000(所影响的行数为 4 行)
*/drop table tb