--處理表重復記錄(查詢和刪除)
/******************************************************************************************************************************************************
1、Num、
Name
相同的重復值記錄,沒有大小關系只保留一條
2、
Name
相同,ID有大小關系時,保留大或小其中一個記錄******************************************************************************************************************************************************/
--1、用於查詢重復處理記錄(如果列沒有大小關系時2000用生成自增列和臨時表處理,SQL2005用row_number函數處理)
--> --> 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最小的記錄(推薦用1,2,3),方法3在SQl05時，效率高於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為唯一時可用):
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
生成結果:
/*
ID
Name
Memo
----------- ---- ----
1 A A1
4 B B1
(2 行受影響)
*/
--II、Name相同ID最大的記錄,與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為唯一時可用):
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
生成結果2:
/*
ID
Name
Memo
----------- ---- ----
3 A A3
5 B B2
(2 行受影響)
*/
--2、刪除重復記錄有大小關系時,保留大或小其中一個記錄
--> --> 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最小的記錄(推薦用1,2,3),保留最小一條
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為唯一時可用):
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
生成結果:
/*
ID
Name
Memo
----------- ---- ----
1 A A1
4 B B1
(2 行受影響)
*/
--II、Name相同ID保留最大的一條記錄:
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為唯一時可用):
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 行受影響)
*/
--3、刪除重復記錄沒有大小關系時，處理重復值
--> --> 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
--排除重復記錄結果集生成臨時表#
truncate
table
#T
--清空表
insert
#T
select
*
from
#
--把臨時表#插入到表#T中
--查看結果
select
*
from
#T
/*
Num
Name
----------- ----
1 A
2 B
(2 行受影響)
*/
--重新執行測試數據后用方法2
方法2:
alter
table
#T
add
ID
int
identity
--新增標識列
go
delete
a
from
#T a
where
exists(
select
1
from
#T
where
Num=a.Num
and
Name
=a.
Name
and
ID>a.ID)
--只保留一條記錄
go
alter
table
#T
drop
column
ID
--刪除標識列
--查看結果
select
*
from
#T
/*
Num
Name
----------- ----
1 A
2 B
(2 行受影響)
*/
--重新執行測試數據后用方法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
--查看結果
select
*
from
#T
/*
Num
Name
----------- ----
1 A
2 B
(2 行受影響)
*/