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MySQL根據某一個或者多個字段查找重復數據的sql語句

sql 查出一張表中重復的所有記錄數據

1.表中有id和name 兩個字段，查詢出name重復的所有數據

 select * from xi a where (a.username) in (select username from xi group by username having count(*) > 1)

2、查詢出所有數據進行分組之后，和重復數據的重復次數的查詢數據，先列下：

 select count(username) as '重復次數',username from xi group by username having count(*)>1 order by username desc

3、一下為查看別人的結果，現列下：查詢及刪除重復記錄的方法大全

1、查找表中多余的重復記錄，重復記錄是根據單個字段（peopleId）來判斷

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

2、刪除表中多余的重復記錄，重復記錄是根據單個字段（peopleId）來判斷，只留有rowid最小的記錄

 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、查找表中多余的重復記錄（多個字段）

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

4、刪除表中多余的重復記錄（多個字段），只留有rowid最小的記錄

 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、查找表中多余的重復記錄（多個字段），不包含rowid最小的記錄

 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)

比方說

在A表中存在一個字段“name”，

而且不同記錄之間的“name”值有可能會相同，

現在就是需要查詢出在該表中的各記錄之間，“name”值存在重復的項；

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

如果還查性別也相同大則如下:

 Select Name,sex,Count(*) From A Group By Name,sex 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＂重復記錄＂有兩個意義上的重復記錄，一是完全重復的記錄，也即所有字段均重復的記錄，二是部分關鍵字段重復的記錄，比如Name字段重復，而其他字段不一定重復或都重復可以忽略。

　　1、對于第一種重復，比較容易解決，使用

 select distinct * from tableName

就可以得到無重復記錄的結果集。　　

如果該表需要刪除重復的記錄（重復記錄保留1條），

可以按以下方法刪除

 select distinct * into #Tmp from tableName
drop table tableName
select * into tableName from #Tmp
drop table #Tmp

發生這種重復的原因是表設計不周產生的，增加唯一索引列即可解決。

2、這類重復問題通常要求保留重復記錄中的第一條記錄，操作方法如下　　假設有重復的字段為Name,Address，要求得到這兩個字段唯一的結果集

 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)

最后一個select即得到了Name，Address不重復的結果集（但多了一個autoID字段，實際寫時可以寫在select子句中省去此列）

(四)查詢重復

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

對一個字段查找重復記錄

根據sample_code字段找到重復記錄

SELECT * FROM tb_table WHERE sample_code IN( SELECT sample_code FROM tb_table GROUP BY sample_code HAVING COUNT(sample_code) > 1 );

對多個字段查找重復記錄（這里以2個為例）

根據name和code字段找到重復記錄

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
)

總結

以上所述是小編給大家介紹的MySQL根據某一個或者多個字段查找重復數據的sql語句，希望對大家有所幫助，如果大家有任何疑問請給我留言，小編會及時回復大家的。在此也非常感謝大家對腳本之家網站的支持！

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