sql 查出一張表中重復的所有記錄數(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)進行分組之后，和重復數(shù)據(jù)的重復次數(shù)的查詢數(shù)據(jù)，先列下：
select count(username) as '重復次數(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(jù)單個字段（peopleId）來判斷
select * from peoplewhere 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(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記錄（多個字段）
select * from vitae awhere (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 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)
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 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)
(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 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
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(guān)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(jié)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 tableNamedrop table tableNameselect * into tableName from #Tmpdrop table #Tmp
發(fā)生這種重復的原因是表設計不周產(chǎn)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(jié)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)
最后一個select即得到了Name，Address不重復的結(jié)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(jù)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(jù)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(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，小編會及時回復大家的。在此也非常感謝大家對VeVb武林網(wǎng)網(wǎng)站的支持！
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