oracle之如何删除表中的重复记录只保留其中一条

Posted 2023-04-20

参考技术A SQL> select * from t;

ID
----------
1
1
2
2
2
3
4
4

8 rows selected.

SQL> select rowid rid,id from t;

RID ID
------------------ ----------
AAAVveAAHAAAAXFAAA 1
AAAVveAAHAAAAXFAAB 1
AAAVveAAHAAAAXFAAC 2
AAAVveAAHAAAAXFAAD 2
AAAVveAAHAAAAXFAAE 2
AAAVveAAHAAAAXFAAF 3
AAAVveAAHAAAAXFAAG 4
AAAVveAAHAAAAXFAAH 4

8 rows selected.

SQL> delete from t where rowid in (select rowid rid from (select row_number() over (partition by id order by id) rn,id from t) where rn<>1);

4 rows deleted.

SQL> select rowid,id from t;

ROWID ID
------------------ ----------
AAAVveAAHAAAAXFAAA 1
AAAVveAAHAAAAXFAAC 2
AAAVveAAHAAAAXFAAF 3
AAAVveAAHAAAAXFAAG 4本回答被提问者和网友采纳 参考技术B 最高效的删除重复记录方法 ( 因为使用了ROWID)
DELETE FROM EMP E WHERE E.ROWID > (SELECT MIN(X.ROWID) FROM EMP X WHERE X.EMP_NO = E.EMP_NO);

笔记：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，重复记录是根据单个字段（Id）来判断

select * from 表 where Id in (select Id from 表 group byId having count(Id) > 1)

 

2、删除表中多余的重复记录，重复记录是根据单个字段（Id）来判断，只留有rowid最小的记录

DELETE from 表 WHERE (判断字段) IN ( SELECT 判断字段 FROM 表 GROUP BY 判断字段 HAVING COUNT(判断字段) > 1) AND ROWID NOT IN (SELECT MIN(ROWID) FROM 表 GROUP BY id HAVING COUNT(*) > 1);

注意：AND后面的句子获取到的是除去拥有rowid最小的所有的记录（单个不重复记录也包含），Where 与 AND之间是获取所有含有重复记录的字段。

 

3、查找表中多余的重复记录（多个字段）

select * from 表 a where (a.Id,a.seq) in(select Id,seq from 表 group by Id,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（原理同2）

delete from 表 a where (a.Id,a.seq) in (select Id,seq from 表 group by Id,seq having count(*) > 1) and rowid not in (select min(rowid) from 表 group by Id,seq having count(*)>1)

示例二：delete from student where s_id not in(select min(s_id) from student group by s_name,c_id);

 

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

select * from 表 a where (a.Id,a.seq) in (select Id,seq from 表 group by Id,seq having count(*) > 1) and rowid not in (select min(rowid) from 表 group by Id,seq having count(*)>1)