[07-04] 处理表重复记录(查询和删除)_整理贴
--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)
*/
