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一、Oracle查询重复数据：
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比如现在有一人员表 (表名：peosons)，若想将姓名、身份证号、住址这三个字段完全相同的记录查询出来
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select p1.*
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from persons p1,persons p2
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where p1.id<>p2.id
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and p1.cardid = p2.cardid and p1.pname = p2.pname and p1.address = p2.address
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可以实现上述效果。
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二、Oracle删除重复数据
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几个删除重复记录的SQL语句
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1.用rowid方法
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2.用group by方法
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3.用distinct方法
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1。用rowid方法
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据据oracle带的rowid属性，进行判断，是否存在重复，语句如下：
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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……)
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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……)
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2.group by方法
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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
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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
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create table table_new as select distinct * from table1 minux
truncate table table1;
insert into table1 select * from table_new;
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三、
查询及删除重复记录的方法大全
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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
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select * from people
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where peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1)
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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
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delete from people
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where peopleId in (select peopleId from people group by peopleId
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having count(peopleId) > 1)
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and rowid not in (select min(rowid) from people group by peopleId having count(peopleId )>1)
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3、查找表中多余的重复记录(多个字段)
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select * from vitae a
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where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)
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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
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delete from vitae a
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where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)
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and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1)
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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
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select * from vitae a
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where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)
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and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1)
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(二)
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比方说
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在A表中存在一个字段“name”，
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而且不同记录之间的“name”值有可能会相同，
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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;
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Select Name,Count(*) From A Group By Name Having Count(*) > 1
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如果还查性别也相同大则如下：
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Select Name,***,Count(*) From A Group By Name,*** Having Count(*) > 1
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(三)
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方法一
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declare @max integer,@id integer
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declare cur_rows cursor local for select 主字段，count(*) from 表名 group by 主字段 having count(*) >; 1
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open cur_rows
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fetch cur_rows into @id,@max
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while @@fetch_status=0
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begin
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select @max = @max -1
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set rowcount @max
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delete from 表名 where 主字段 = @id
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fetch cur_rows into @id,@max
