查询和删除表中重复数据

查询和删除表中重复数据

文章分类:数据库?

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?

select ? p1.* ? from ? persons ? p1,persons ? p2 ? where ? p1.id<>p2.id ? 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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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:?

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?? ? 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：?

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?? ?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:?

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　　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：?

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　　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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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?

select * from people?

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?

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)?

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sql server不支持rowid?

我们可以变通实现同样的效果?

eg:?

delete from t_serviceitem?

where servid in (select servid from t_serviceitem group by servid having count(servid)>1)?

and gid not in (select min(gid) from t_serviceitem group by servid having count(servid )>1)?

(gid是该表PK)?

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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)?

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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?

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)?

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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?

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)?

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(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?

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(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?

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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