处理表重复记录(查询和删除)

摘自:

http://topic.csdn.net/u/20080626/00/43d0d10c-28f1-418d-a05b-663880da278a.html?85256

多谢这位大哥

--
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)

*/