Oracle删除重复行
分类： ORACLE2010-12-12 17:10 423人阅读 评论(0) 收藏 举报
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查询及删除重复记录的SQL语句
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)
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)
注:rowid为oracle自带不用该.....
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
＂重复记录＂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)
=======================================
1。用rowid方法
据据Oracle带的rowid属性，进行判定，是否存在重复,语句如下：
查数据:
select
* from table1 a where rowid !=(select max(rowid)
from table1 b
where a.name1=b.name1 and
a.name2=b.name2......)
删数据：
delete from table1 a where rowid
!=(select max(rowid)
from table1 b where a.name1=b.name1 and
a.name2=b.name2......)
2.group by方法
查数据:
select count(num),
max(name) from student --列出重复的记录数，并列出他的name属性
group by num
having
count(num) >1 --按num分组后找出表中num列重复，即出现次数大于一次
删数据：
delete from
student
group by num
having count(num) >1
这样的话就把所有重复的都删除了。
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3.用distinct方法
-对于小的表比较有用
create table table_new as select
distinct * from table1 minux
truncate table table1;
insert into
table1 select * from table_new;