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) */
if object_id('tb') is not null drop table tb; go create table tb ( name int, value varchar(3), time datetime ) insert into tb select 135888,'aa1','2012/2/20 8:37' union all select 135888,'aa2','2012/2/20 8:37' union all select 135888,'bb1','2012/3/20 8:37' union all select 135888,'bb2','2012/3/20 8:37' union all select 207558,'cc1','2012/4/20 8:37' union all select 207558,'cc2','2012/4/20 8:37' union all select 207558,'dd1','2012/5/20 8:37' union all select 207558,'dd2','2012/5/20 8:37' select t.* from tb t where t.time =(select max(time) from tb where t.name=name)name value time ----------- ----- ----------------------- 207558 dd1 2012-05-20 08:37:00.000 207558 dd2 2012-05-20 08:37:00.000 135888 bb1 2012-03-20 08:37:00.000 135888 bb2 2012-03-20 08:37:00.000(4 行受影响)
create table yan (name int, value varchar(5), times datetime)insert into yan select 135888, 'AA1', '2012/2/20 8:37' union all select 135888, 'AA2', '2012/2/20 8:37' union all select 135888, 'BB1', '2012/3/31 14:40' union all select 135888, 'BB2', '2012/3/31 14:40' union all select 207558, 'CC1', '2012/1/11 12:32' union all select 207558, 'CC2', '2012/1/11 12:32' union all select 207558, 'DD1', '2012/2/23 17:01' union all select 207558, 'DD2', '2012/2/23 17:01' with t as (select name,value,times, dense_rank() over(partition by name order by times desc) rn from yan ) select name,value,times from t where rn=1 name value times ----------- ----- ----------------------- 135888 BB1 2012-03-31 14:40:00.000 135888 BB2 2012-03-31 14:40:00.000 207558 DD1 2012-02-23 17:01:00.000 207558 DD2 2012-02-23 17:01:00.000(4 row(s) affected)
1L的虽然字段名Time 写成了Name, 但是效率真快。
select t.* from tb t where t.time =(select max(time) from tb where t.name=name) 这句我要写成 select t.* from tb t where t.time IN (select max(time) from tb where t.name=name) 才能通过,我用的是SqlCe,不知道有没有关系
where not exists(select 1 from t where name=t.name and time>t.name)
where not exists(select 1 from t where name=t.name and Time>t.Time)
where Time=(select max(Time) from t where name=t.name)
/******************************************************************************************************************************************************
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)
*/
if object_id('tb') is not null
drop table tb;
go
create table tb
(
name int,
value varchar(3),
time datetime
)
insert into tb
select 135888,'aa1','2012/2/20 8:37' union all
select 135888,'aa2','2012/2/20 8:37' union all
select 135888,'bb1','2012/3/20 8:37' union all
select 135888,'bb2','2012/3/20 8:37' union all
select 207558,'cc1','2012/4/20 8:37' union all
select 207558,'cc2','2012/4/20 8:37' union all
select 207558,'dd1','2012/5/20 8:37' union all
select 207558,'dd2','2012/5/20 8:37' select t.* from tb t where t.time =(select max(time) from tb where t.name=name)name value time
----------- ----- -----------------------
207558 dd1 2012-05-20 08:37:00.000
207558 dd2 2012-05-20 08:37:00.000
135888 bb1 2012-03-20 08:37:00.000
135888 bb2 2012-03-20 08:37:00.000(4 行受影响)
create table yan
(name int, value varchar(5), times datetime)insert into yan
select 135888, 'AA1', '2012/2/20 8:37' union all
select 135888, 'AA2', '2012/2/20 8:37' union all
select 135888, 'BB1', '2012/3/31 14:40' union all
select 135888, 'BB2', '2012/3/31 14:40' union all
select 207558, 'CC1', '2012/1/11 12:32' union all
select 207558, 'CC2', '2012/1/11 12:32' union all
select 207558, 'DD1', '2012/2/23 17:01' union all
select 207558, 'DD2', '2012/2/23 17:01'
with t as
(select name,value,times,
dense_rank() over(partition by name order by times desc) rn
from yan
)
select name,value,times from t where rn=1
name value times
----------- ----- -----------------------
135888 BB1 2012-03-31 14:40:00.000
135888 BB2 2012-03-31 14:40:00.000
207558 DD1 2012-02-23 17:01:00.000
207558 DD2 2012-02-23 17:01:00.000(4 row(s) affected)
select t.* from tb t where t.time =(select max(time) from tb where t.name=name)
这句我要写成
select t.* from tb t where t.time IN (select max(time) from tb where t.name=name)
才能通过,我用的是SqlCe,不知道有没有关系