MySQL根据某一个或者多个字段查找重复数据的sql语句

2024-01-26 17:28| 来源: 网络整理| 查看: 265

1.表中有id和name 两个字段，查询出name重复的所有数据

1 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：

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

3、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

1 2 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

1 2 3 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）

1 2 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

1 2 3 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

1 2 3 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；

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

如果还查性别也相同大则如下:

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

(三)

方法一

1 2 3 4 5 6 7 8 9 10 11 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

1 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

1 2 3 4 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

1 2 3 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

1 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

1 SELECT * FROM tb_table WHERE sample_code IN( SELECT sample_code FROM tb_table GROUP BY sample_code HAVING 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

1 2 3 4 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 )

多字段查，删

查

SELECT * FROM vip_goodsdiscount WHERE (goodsId,cardType) IN (SELECT goodsId,cardType FROM vip_goodsdiscount GROUP BY goodsId,cardType HAVING COUNT(*) > 1)ORDER BY goodsId DESC

删

DELETE FROM vip_goodsdiscount WHERE (vip_goodsdiscount.goodsId,vip_goodsdiscount.cardType) IN (SELECT * FROM (SELECT goodsId,cardType FROM vip_goodsdiscount GROUP BY goodsId,cardType HAVING COUNT(*) > 1) AS t1 ) AND id NOT IN (SELECT * FROM (SELECT MIN(id) FROM vip_goodsdiscount GROUP BY goodsId,cardType HAVING COUNT(*)>1) AS t2)

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