Oracle查询表里的重复数据方法_oracle_脚本之家

作者:分分快三全天计划网站

2、删除表中多余的重复记录(多个字段卡塔 尔(阿拉伯语:قطر‎,只留有id最小的记录

delete from student a
where (a.username,a.seq) in (select username,seq from (select username,seq from a group by username,seq having count(*) > 1)  t1)
and id not in ( select id from (select min(id) from vitae group by username,seq having count(*)>1) t2)

参谋小说:

假如还查性别也如出风流倜傥辙大则如下:

3卡塔尔国删除 重复项中id最大的记录

1、删除表中多余的重复记录,重复记录是username推断,只留有id最小的记录

 

delete from studentwhere
username in ( select username from studentgroup by username having count(username)>1)
and id not in (select min(id) as id from studentgroup by username having count(username)>1 )

(上边那条语句在mysql中履行会报错:

试行报错:1093 - You can't specify target table 'student' for update in FROM clause

缘由是:更新数据时选择了查询,而查询的数额又做了改正的规格,mysql不支持这种格局。oracel和msserver都扶助这种方法。

怎么走避那一个标题?

再加豆蔻年华层封装,

delete from student where
username in (select username from ( select username from student group by username having count(username)>1) a)
and id not in ( select id from (select min(id) as id from student group by username having count(username)>1 ) b)

 注意select min(id) 后边要有as id.

骨子里还会有更简短的主意(针对单个字段卡塔尔:

delete from student where
id not in (select id from (select min(id) as id from student group by username) b);

 

拓展:

假若还查性别也长期以来大则如下:

 

很可惜那时候并未有做出来,回家寻觅了风流浪漫番,发掘利用子查询的能够便捷减轻。

delete from studentgroup by numhaving count >1

 

 面试境遇多少个MySQl的珠璧交辉的主题材料,怎么样从student表中删去重复名字的行,并保存最小id的笔录?

select a.rowid,a.* from 表名 a where a.rowid !=  from 表名 b where a.字段1 = b.字段1 and a.字段2 = b.字段2 )

 

一、背景

成立索引

末尾一个select即获得了Name,Address不另行的结果集(但多了三个autoID字段,实际写时能够写在select子句中节省此列卡塔尔国查询重复

中央办法能够参照他事他说加以考查前面包车型客车依赖的资料,可是由于mysql不支持同临时候对贰个表张开操作,即子查询和要扩充的操作不能够是同一个表,由此必要经过零时表中间转播一下。

select * from vitae awhere  in (select peopleId,seq from vitae group by peopleId,seq having countand rowid not in  from vitae group by peopleId,seq having count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

 

经过,我们要刨除重复数据,只保留最新的一条数据,就足以那样写了:

 

delete from vitae a where  in (select tableId,seq from vitae group by tableId,seq having countand rowid not in  from vitae group by tableId,seq having count

 

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

3、查找表中多余的重复记录(三个字段卡塔尔国 select * from vitae a where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)

依据id分组并计数,有个别id号那少年老成组的数额超过1条则感到重新。

 

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

实行中发觉上边包车型地铁删除字段重复的艺术,由于还不可能为多字段重新建构索引,导致数据量大时效用超级低,低到不能忍受。最终,受不了等了半天没反应的风貌,本身决定,不落窠臼。

delete from vitae awhere  in (select peopleId,seq from vitae group by peopleId,seq having countand rowid not in  from vitae group by peopleId,seq having count

假造到,估算同豆蔻梢头记录的双重次数极低。日常为2,或3,重复次数相比较聚焦。所以能够尝尝直接删除重复项中最大的,直到删除到不重复,那个时候其id自然也是当下再一次的中间最小的。

3、查找表中多余的重复记录

create index indexid on tmprelationship_id

Oracle删除重复数据的SQL:

 

查询及删除重复记录的不二等秘书籍大全1、查找表中多余的重复记录,重复记录是依照单个字段来判断

删除

INSERT INTO t_table_bakselect distinct * from t_table;

 

举例现在有一人员表 若想将姓名、身份ID号、住址那四个字段完全相符的笔录查询出来

2.1日常方法

那样的话就把全体重复的都剔除了。3.用distinct方法 -对于小的表相比有用

询问及删除重复记录的点子

select * from table where tableId in (select tableId from table group by tableId having count

 

PS:将地点的>号改为=号就足以查询出从未重新的数码了。

2.多字段重复

select id from group by id having count > 1

 

理当如此,上面语句的推行效能是非常低的,能够设想创设偶然表,讲供给看清重复的字段、rowid插入不时表中,然后删除的时候在进行比较。

 

select p1.*from persons p1,persons p2where p1.id<>p2.idand p1.cardid = p2.cardid and p1.pname = p2.pname and p1.address = p2.address

create table tmpuid as (select uid from userinfo group by uid having count(uid))

select * from vitae awhere  in (select peopleId,seq from vitae group by peopleId,seq having count

 

Oracle删除重复数据的SQL:

create index indexid on tmprelation_id2

oracle查询表中字段里多少是或不是有再次

 

能够完成上述意义。多少个删除重复记录的SQL语句1.用rowid方法2.用group by方法3.用distinct方法1。用rowid方法据据oracle带的rowid属性,进行推断,是不是存在重复,语句如下:查数据:

2.2 实施出真知

delete from 表名 a where 字段1,字段2 in(select 字段1,字段2,count from 表名 group by 字段1,字段2 having count

 

想要删除那几个再一次的多少,能够使用下边语句进行删减

drop table tmprelationid2

select * from vitae a where  in (select tableId,seq from vitae group by tableId,seq having count

delete from relationship where id not in (select id from tmprelationshipid) and (source,target) in (select source,target from relationship)

select 字段1,字段2,count from 表名 group by 字段1,字段2 having count > 1

 

4、删除表中多余的重复记录,只留有rowid最小的记录

4卡塔尔删除不常表

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

 

主意二"重复记录"有八个意思上的重复记录,一是一点一滴重复的记录,也即全体字段均再度的笔录,二是一些第一字段重复的记录,比如Name字段重复,而其它字段不必然再度或都重新能够忽视。1、对于第少年老成种重复,比较便于解决,使用select distinct * from tableName就足以获取无重复记录的结果集。倘若该表须要删除重复的记录,能够按以下情势删除

 

select * from vitae a where  in (select tableId,seq from vitae group by tableId,seq having count and rowid not in  from vitae group by tableId,seq having count

 

5、查找表中剩下的重复记录,不含有rowid最小的笔录

 

对此截然重复记录的删除

create index indexid on tmpid

今昔正是内需查询出在该表中的各记录之间,“name”值存在重复的项;

 

选取ROWID查询重复数据:

 

3、查找表中剩下的重复记录

更改表user_info的主键uid为自增的id后,忘了安装原本主键uid属性为unique,结果导致暴发uid重复的笔录。为此必要清理...

delete from 表名 a where a.rowid !=  from 表名 b where a.字段1 = b.字段1 and a.字段2 = b.字段2 )

delete tab t where t.rowid >  from tab t2 where t.col2 = t2.col2 and t.col8 = t2.col8)

2、删除表中多余的重复记录,重复记录是依据单个字段(peopleId卡塔尔国来推断,只留有rowid最小的笔录 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)

2.group by方式查数据:select count from student --列出重新的记录数,并列出她的name属性group by numhaving count >1 --按num分组后找寻表中num列重复,即现身次数超过一回删数码:

 

select * from 表 where Id in (select Id from 表 group byId having count

 

5、查找表中多余的重复记录,不含有rowid最小的记录

 

4、删除表中多余的重复记录,只留有rowid最小的笔录

delete from user_info where id not in (select id from tmp_id) and uid in (select uid from tmp_uid)

在A表中存在三个字段“name”,而且差别记录之间的“name”值有一点都不小希望会一直以来,

 

2、删除表中多余的重复记录,重复记录是依照单个字段来剖断,只留有rowid最小的笔录。

(风度翩翩) 1、查找表中剩下的重复记录,重复记录是依附单个字段(peopleId卡塔尔国来判定select * from people where peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1)

上边就能够张开那样的删减操作了:

create table tmprelationid2 as (select max(id) from relationship group by source,target having count(*)>1)

select distinct * from 表名

退换零时表

4、删除表中多余的重复记录,只留有rowid最小的笔录

 

Oracle查询重复数据并删除,只保留一条记录1、查找表中多余的重复记录,重复记录是依照单个字段来决断

 

MySQL查询及删除重复记录的方法查询及删除重复记录的办法

create table tmpid as (select min(id) from userinfo group by uid having count(uid))

CREATE TABLE 临时表 AS (select 字段1,字段2,count from 表名 group by 字段1,字段2 having count

 

delete from peoplewhere peopleId in (select peopleId from people group by peopleIdhaving countand rowid not in  from people group by peopleId having count

由uid的重新直接的变成了relationship中的记录重复,故继续去重。先介绍健康管理流程,在介绍自己依照作者数据特点施行的愈益可行的艺术!

1、查找表中剩下的重复记录,重复记录是依据单个字段来判断

数据量大时必必要为uid创立索引

提出先将查询到的再一次的数据插入到二个偶尔表中,然后对开展删减,那样,实施删除的时候就毫无再实行叁次查询了。如下:

 

SELECT TEST_NAME,COUNT FROM T_TEST GROUP BY TEST_NAME HAVING COUNT > 1

 

地方那句话就是起家了有时表,并将查询到的数据插入个中。

delete from relationship where id in (select id from tmprelationid2)

select * from table1 a where rowid !=from table1 b where a.name1=b.name1 and a.name2=b.name2……)

delete from table1 a where rowid !=from table1 b where a.name1=b.name1 and a.name2=b.name2……)

 

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

 

3、查找表中多余的重复记录

 

Select Name,***,Count From A Group By Name,*** Having Count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 >; 1open cur_rowsfetch cur_rows into @id,@maxwhile @@fetch_status=0beginselect @max = @max -1set rowcount @maxdelete from 表名 where 主字段 = @idfetch cur_rows into @id,@maxendclose cur_rowsset rowcount 0

 

select * from 表 a where  in(select Id,seq from 表 group by Id,seq having count

4、删除表中多余的重复记录(多少个字段卡塔尔,只留有rowid最小的记录 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)

delete from 表名 a where 字段1,字段2 in (select 字段1,字段2 from 临时表);

mysql中数量去重和优化

6、查询出二个表中,某一列的值是如出风流倜傥辙的SQL:

大概流程如下:

delete from table where tableId in (select tableId from table group by tableId having count and rowid not in  from table group by tableId having count

 

二、解决

1卡塔 尔(阿拉伯语:قطر‎选取每种重复项中id最大的多个记录

可以将查询的笔录停放有的时候表中,然后再将本来的表记录删除,最终将有的时候表的数据导回原本的表中。如下:

主干的同地点:

DELETE from 表 WHERE  IN ( SELECT id FROM 表 GROUP BY id HAVING COUNT AND ROWID NOT IN  FROM 表 GROUP BY id HAVING COUNT;

create table tmprelationshipid as (select min(id) as id from relationship group by source,target having count(*)>1)

select * from 表 a where  in (select Id,seq from 表 group by Id,seq having count and rowid not in  from 表 group by Id,seq having count

2卡塔 尔(英语:State of Qatar)创制索引(仅需在首先次时实施卡塔 尔(英语:State of Qatar)

create table table_new as select distinct * from table1 minuxtruncate table table1;insert into table1 select * from table_new;

 

CREATE TABLE 临时表 AS (select distinct * from 表名); truncate table 正式表; insert into 正式表 ;drop table 临时表;

create index indexuid on tmpuid

2、删除表中多余的重复记录,重复记录是遵照单个字段来决断,只留有rowid最小的笔录

删去多余的重复记录,保留重复项中id最小的

一张person表,有id和name的五个字段,id是独步一时的不允许再次,id相似则认为是再次的记录。

 

oracle中,有个藏匿了电动rowid,里面给每条记下二个唯意气风发的rowid,大家假诺想保留最新的一条记下,大家就足以使用那些字段,保留重复数据中rowid最大的一条记下就足以了。

写在头里:数据量大时,一定要多涉及的要紧字段创立索引!!!不然一点也不快不快比异常的慢,慢到想死的心都有了

Select Name,Count From A Group By Name Having Count > 1

浮动零时表,在那之中uid是内需去重的字段

括号中的SQL查询出rowid最大的笔录,而外界就是查询出除了rowid最大之外的此外重复的数量了。

 

select * from peoplewhere peopleId in (select peopleId from people group by peopleId having count

 

create table 临时表 as select a.字段1,a.字段2,MAX dataid from 正式表 a GROUP BY a.字段1,a.字段2; delete from 表名 a where a.rowid != (select b.dataid from 临时表 b where a.字段1 = b.字段1 and a.字段2 = b.字段2 );commit;

重新上述手续1卡塔 尔(阿拉伯语:قطر‎,2卡塔 尔(阿拉伯语:قطر‎,3卡塔 尔(英语:State of Qatar),4卡塔 尔(英语:State of Qatar),直到创设的不时表中不真实记录就甘休(对于再次次数的数量,相比较飞速卡塔 尔(阿拉伯语:قطر‎

2、删除表中多余的重复记录,重复记录是根据单个字段来决断,只留有rowid最小的记录

create table tmp_relation as (select source,target from relationship group by source,target having count(*)>1)

delete from 表 a where  in (select Id,seq from 表 group by Id,seq having count and rowid not in  from 表 group by Id,seq having count

更改表user_info的主键uid为自增的id后,忘了安装原来主键uid属性为unique,结果产生发生uid重复的笔录。为此必要清理后来布置的重复记录。

5、查找表中多余的重复记录,不含有rowid最小的记录

 

地点的SQL注意:语句特别轻巧,就是将查询到的数据删除掉。可是这种删除试行的频率异常低,对于大数据量来讲,只怕会将数据库吊死。

 

对于表中两行记录完全风姿浪漫致的意况,能够用上面语句获取到去掉重复数据后的记录:

1 单字段重复

除去重复数据的主导构造写法:

发出这种重新的来头是表设计不周发生的,扩张独一索引列就可以缓和。2、这类重复难题普通须求保存重复记录中的第一条记下,操作方法如下假如有重复的字段为Name,Address,必要得到那八个字段唯生龙活虎的结果集

万大器晚成想删除几个表的重新数据,可以先建三个不时表,将去掉重复数据后的数据导入到有的时候表,然后在从有时表将数据导入正式表中,如下:

本文由分分快三计划发布,转载请注明来源

关键词: 分分快三计划 方法 脚本 表里 之家