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MySQL根據(jù)某一個或者多個字段查找重復(fù)數(shù)據(jù)的sql語句

發(fā)布時間:2020-10-09 14:53:13 來源:腳本之家 閱讀:218 作者:faceAJ 欄目:MySQL數(shù)據(jù)庫

sql 查出一張表中重復(fù)的所有記錄數(shù)據(jù)

1.表中有id和name 兩個字段,查詢出name重復(fù)的所有數(shù)據(jù)

 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(shù)據(jù)進(jìn)行分組之后,和重復(fù)數(shù)據(jù)的重復(fù)次數(shù)的查詢數(shù)據(jù),先列下:

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

3、一下為 查看別人的 結(jié)果,現(xiàn)列下:查詢及刪除重復(fù)記錄的方法大全

1、查找表中多余的重復(fù)記錄,重復(fù)記錄是根據(jù)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(fù)記錄,重復(fù)記錄是根據(jù)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(fù)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(fù)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(fù)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(xiàn)在就是需要查詢出在該表中的各記錄之間,“name”值存在重復(fù)的項(xiàng);

 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(fù)記錄"有兩個意義上的重復(fù)記錄,一是完全重復(fù)的記錄,也即所有字段均重復(fù)的記錄,二是部分關(guān)鍵字段重復(fù)的記錄,比如Name字段重復(fù),而其他字段不一定重復(fù)或都重復(fù)可以忽略。

  1、對于第一種重復(fù),比較容易解決,使用

 select distinct * from tableName

就可以得到無重復(fù)記錄的結(jié)果集?! ?/p>

如果該表需要刪除重復(fù)的記錄(重復(fù)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(fā)生這種重復(fù)的原因是表設(shè)計不周產(chǎn)生的,增加唯一索引列即可解決。

2、這類重復(fù)問題通常要求保留重復(fù)記錄中的第一條記錄,操作方法如下  假設(shè)有重復(fù)的字段為Name,Address,要求得到這兩個字段唯一的結(jié)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(fù)的結(jié)果集(但多了一個autoID字段,實(shí)際寫時可以寫在select子句中省去此列)

(四)查詢重復(fù)

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

對一個字段查找重復(fù)記錄

MySQL根據(jù)某一個或者多個字段查找重復(fù)數(shù)據(jù)的sql語句

根據(jù)sample_code字段找到重復(fù)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(fù)記錄(這里以2個為例)

MySQL根據(jù)某一個或者多個字段查找重復(fù)數(shù)據(jù)的sql語句

根據(jù)name和code字段找到重復(fù)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(jié)

以上所述是小編給大家介紹的MySQL根據(jù)某一個或者多個字段查找重復(fù)數(shù)據(jù)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(fù)大家的。在此也非常感謝大家對億速云網(wǎng)站的支持!

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