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)

 select count(username) as '重复次数',username from xi group by username having count(*)>1 order by username desc

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 peoplewhere peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1)

 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)

 select * from vitae awhere (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)

 delete from vitae awhere (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)

 select * from vitae awhere (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)

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

 Select Name,sex,Count(*) From A Group By Name,sex Having Count(*) > 1

方法一

declare @max integer,@id integerdeclare 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=0begin select @max = @max -1 set rowcount @max delete from 表名 where 主字段 = @idfetch cur_rows into @id,@maxendclose cur_rowsset rowcount 0

　　1、对于第一种重复，比较容易解决，使用

 select distinct * from tableName

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 tableNamedrop table tableNameselect * into tableName from #Tmpdrop table #Tmp

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 tableNameselect min(autoID) as autoID into #Tmp2 from #Tmp group by Name,autoIDselect * from #Tmp where autoID in(select autoID from #tmp2)

(四)查询重复

 select * from tablename where id in (select id from tablenamegroup by idhaving count(id) > 1)

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 HAVING COUNT(sample_code) > 1 );

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 HAVING count(nameAndCode) > 1)

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