SQL重复记录查询
1
、查找表中多余的重复记录，重复记录是根据单个字段（peopleId）来判断
select
*
from
people
where
peopleId
in
(
select
peopleId
from
people
group
by
peopleId
having
count
(peopleId)
>
1
)
例二：
select
*
from
testtable
where
numeber
in
(
select
number
from
people
group
by
number
having
count
(
number
)
>
1
)
可以查出testtable表中number相同的记录
2
、删除表中多余的重复记录，重复记录是根据单个字段（peopleId）来判断，只留有rowid最小的记录
delete
from
people
where
peopleId
in
(
select
peopleId
from
people
group
by
peopleId
having
count
(peopleId)
>
1
)
and
rowid
not
in
(
select
min
(rowid)
from
people
group
by
peopleId
having
count
(peopleId )
>
1
)
3
、查找表中多余的重复记录（多个字段）
select
*
from
vitae a
where
(a.peopleId,a.seq)
in
(
select
peopleId,seq
from
vitae
group
by
peopleId,seq
having
count
(
*
)
>
1
)
4
、删除表中多余的重复记录（多个字段），只留有rowid最小的记录
delete
from
vitae a
where
(a.peopleId,a.seq)
in
(
select
peopleId,seq
from
vitae
group
by
peopleId,seq
having
count
(
*
)
>
1
)
and
rowid
not
in
(
select
min
(rowid)
from
vitae
group
by
peopleId,seq
having
count
(
*
)
>
1
)
5
、查找表中多余的重复记录（多个字段），不包含rowid最小的记录
select
*
from
vitae a
where
(a.peopleId,a.seq)
in
(
select
peopleId,seq
from
vitae
group
by
peopleId,seq
having
count
(
*
)
>
1
)
and
rowid
not
in
(
select
min
(rowid)
from
vitae
group
by
peopleId,seq
having
count
(
*
)
>
1
)
(二)
比方说
在A表中存在一个字段“name”，
而且不同记录之间的“name”值有可能会相同，
现在就是需要查询出在该表中的各记录之间，“name”值存在重复的项；
Select
Name,
Count
(
*
)
From
A
Group
By
Name
Having
Count
(
*
)
>
1
如果还查性别也相同大则如下:
Select
Name,sex,
Count
(
*
)
From
A
Group
By
Name,sex
Having
Count
(
*
)
>
1
(三)
方法一
declare
@max
integer
,
@id
integer
declare
cur_rows
cursor
local
for
select
主字段,
count
(
*
)
from
表名
group
by
主字段
having
count
(
*
)
>
；
1
open
cur_rows
fetch
cur_rows
into
@id
,
@max
while
@@fetch_status
=
0
begin
select
@max
=
@max
-
1
set
rowcount
@max
delete
from
表名
where
主字段
=
@id
fetch
cur_rows
into
@id
,
@max
end
close
cur_rows
set
rowcount
0
方法二
有两个意义上的重复记录，一是完全重复的记录，也即所有字段均重复的记录，二是部分关键字段重复的记录，比如Name字段重复，而其他字段不一定重复或都重复可以忽略。
1
、对于第一种重复，比较容易解决，使用
select
distinct
*
from
tableName
就可以得到无重复记录的结果集。
如果该表需要删除重复的记录（重复记录保留1条），可以按以下方法删除
select
distinct
*
into
#Tmp
from
tableName
drop
table
tableName
select
*
into
tableName
from
#Tmp
drop
table
#Tmp
发生这种重复的原因是表设计不周产生的，增加唯一索引列即可解决。
2
、这类重复问题通常要求保留重复记录中的第一条记录，操作方法如下
假设有重复的字段为Name,Address，要求得到这两个字段唯一的结果集
select
identity
(
int
,
1
,
1
)
as
autoID,
*
into
#Tmp
from
tableName
select
min
(autoID)
as
autoID
into
#Tmp2
from
#Tmp
group
by
Name,autoID
select
*
from
#Tmp
where
autoID
in
(
select
autoID
from
#tmp2)
最后一个select即得到了Name，Address不重复的结果集（但多了一个autoID字段，实际写时可以写在select子句中省去此列）
(四)
查询重复
select
*
from
tablename
where
id
in
(
select
id
from
tablename
group
by
id
having
count
(id)
>
1
)
select * from debt where Studentnumber in(select Studentnumber from debt group by Studentnumber having COUNT(Studentnumber) >1)
select * from debt where Studentnumber in(select Studentnumber from debt group by Studentnumber having COUNT(Studentnumber) >1) and Studentname!=Studentname