MySQL根据某一个或者多个字段查找重复数据的sql语句

sql 查出一张表中重复的所有记录数据


1.表中有id和name 两个字段，查询出name重复的所有数据

select * from xi a where (a.username) in (select username from xi group by username having count(*) > 1)2、查询出所有数据进行分组之后，和重复数据的重复次数的查询数据，先列下：

select count(username) as ‘重复次数’,username from xi group by username having count(*)>1 order by username desc3、一下为 查看别人的 结果，现列下：查询及删除重复记录的方法大全

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)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,sеx,Count(*) From A Group By Name,sеx 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(*) >;

open cur_rows fetch cur_rows into @id,@maxwhile @@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,@maxend

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)　</pre>

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<p>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）</p>

<p>(四)查询重复</p>

<div class=”jb51code”>

<pre class=”brush:sql;”>

select * from tablename where id in (select id from tablenamegroup by idhaving count(id) > 1)对一个字段查找重复记录

根据sample_code字段找到重复记录

SELECT * FROM tb_table WHERE sample_code IN( SELECT sample_code FROM tb_table GROUP BY sample_code HАVING COUNT(sample_code) > 1 );对多个字段查找重复记录（这里以2个为例）

根据name和code字段找到重复记录

SELECT * from (SELECT *, CONCAT(name,code) as nameAndCode from tb_table) t WHERE t.nameAndCode in

(

SELECT nameAndCode from (SELECT CONCAT(name,code) as nameAndCode from tb_table) tt GROUP BY nameAndCode HАVING count(nameAndCode) > 1

)
总结

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