我正在Oracle中进行测试，并用一些示例数据填充了表，但是在此过程中，我不小心加载了重复的记录，因此现在无法使用某些列创建主键。

如何删除所有重复的行并仅保留其中之一？

使用rowid伪列。

DELETE FROM your_table
WHERE rowid not in
(SELECT MIN(rowid)
FROM your_table
GROUP BY column1, column2, column3);

其中column1，column2和column3组成每个记录的标识键。您可能会列出所有列。

从问汤姆

delete from t
 where rowid IN ( select rid
                    from (select rowid rid, 
                                 row_number() over (partition by 
                         companyid, agentid, class , status, terminationdate
                                   order by rowid) rn
                            from t)
                   where rn <> 1);

（修复了丢失的括号）

从DevX.com：

DELETE FROM our_table
WHERE rowid not in
(SELECT MIN(rowid)
FROM our_table
GROUP BY column1, column2, column3...) ;

其中column1，column2等是要使用的键。

DELETE FROM tablename a
      WHERE a.ROWID > ANY (SELECT b.ROWID
                             FROM tablename b
                            WHERE a.fieldname = b.fieldname
                              AND a.fieldname2 = b.fieldname2)

解决方案1）

delete from emp
where rowid not in
(select max(rowid) from emp group by empno);

解决方案2）

delete from emp where rowid in
               (
                 select rid from
                  (
                    select rowid rid,
                      row_number() over(partition by empno order by empno) rn
                      from emp
                  )
                where rn > 1
               );

解决方案3）

delete from emp e1
         where rowid not in
          (select max(rowid) from emp e2
           where e1.empno = e2.empno ); 

创建表t2作为选择与t1不同的*；

您应该使用游标进行循环来做一个小的pl / sql块，并删除您不想保留的行。例如：

declare
prev_var my_table.var1%TYPE;

begin

for t in (select var1 from my_table order by var 1) LOOP

-- if previous var equal current var, delete the row, else keep on going.
end loop;

end;

要选择重复项，仅查询格式可以是：

SELECT GroupFunction(column1), GroupFunction(column2),..., 
COUNT(column1), column1, column2...
FROM our_table
GROUP BY column1, column2, column3...
HAVING COUNT(column1) > 1

因此，根据其他建议的正确查询是：

DELETE FROM tablename a
      WHERE a.ROWID > ANY (SELECT b.ROWID
                             FROM tablename b
                            WHERE a.fieldname = b.fieldname
                              AND a.fieldname2 = b.fieldname2
                              AND ....so on.. to identify the duplicate rows....)

该查询将在数据库中保留最古老的记录，以用于中选择的标准WHERE CLAUSE。

Oracle认证助理（2008）

真正大桌子的最快方法

1. 创建具有以下结构的异常表：exceptions_table

   ROW_ID ROWID
   OWNER VARCHAR2(30)
   TABLE_NAME VARCHAR2(30)
   CONSTRAINT VARCHAR2(30)

2. 尝试创建唯一的约束或主键，这些约束或主键将被重复项所违反。您将收到一条错误消息，因为您有重复项。例外表将包含重复行的行ID。

   alter table add constraint
   unique --or primary key
   (dupfield1,dupfield2) exceptions into exceptions_table;

3. 通过rowid将表与exceptions_table联接在一起，并删除重复项

   delete original_dups where rowid in (select ROW_ID from exceptions_table);

4. 如果要删除的行数很大，则创建一个新表（包含所有授予和索引），并按rowid与exceptions_table反连接，然后将原始表重命名为original_dups表，并将new_table_with_no_dups重命名为原始表

   create table new_table_with_no_dups AS (
       select field1, field2 ........ 
       from original_dups t1
       where not exists ( select null from exceptions_table T2 where t1.rowid = t2.row_id )
   )

使用rowid-

delete from emp
 where rowid not in
 (select max(rowid) from emp group by empno);

使用自我加入-

delete from emp e1
 where rowid not in
 (select max(rowid) from emp e2
 where e1.empno = e2.empno );

解决方案4）

 delete from emp where rowid in
            (
             select rid from
                (
                  select rowid rid,
                  dense_rank() over(partition by empno order by rowid
                ) rn
             from emp
            )
 where rn > 1
);

1.解决方案

delete from emp
    where rowid not in
    (select max(rowid) from emp group by empno);

2.偷偷摸摸

delete from emp where rowid in
               (
                 select rid from
                  (
                    select rowid rid,
                      row_number() over(partition by empno order by empno) rn
                      from emp
                  )
                where rn > 1
               );

3.解决方案

delete from emp e1
         where rowid not in
          (select max(rowid) from emp e2
           where e1.empno = e2.empno ); 

4.解决方案

 delete from emp where rowid in
            (
             select rid from
                (
                  select rowid rid,
                  dense_rank() over(partition by empno order by rowid
                ) rn
             from emp
            )
 where rn > 1
);

5.解决方案

delete from emp where rowid in 
    (
      select  rid from
       (
         select rowid rid,rank() over (partition by emp_id order by rowid)rn from emp     
       )
     where rn > 1
    );

DELETE from table_name where rowid not in (select min(rowid) FROM table_name group by column_name);

您还可以通过其他方式删除重复的记录

DELETE from table_name a where rowid > (select min(rowid) FROM table_name b where a.column=b.column);

create table abcd(id number(10),name varchar2(20))

insert into abcd values(1,'abc')

insert into abcd values(2,'pqr')


insert into abcd values(3,'xyz')

insert into abcd values(1,'abc')

insert into abcd values(2,'pqr')

insert into abcd values(3,'xyz')


select * from abcd
id  Name
1   abc
2   pqr
3   xyz
1   abc
2   pqr
3   xyz

Delete Duplicate record but keep Distinct Record in table 

DELETE 
FROM abcd a
WHERE ROWID > (SELECT MIN(ROWID) FROM abcd b
WHERE b.id=a.id
);

run the above query 3 rows delete 

select * from abcd

id  Name 
1   abc
2   pqr
3   xyz

DELETE FROM tableName  WHERE ROWID NOT IN (SELECT   MIN (ROWID) FROM table GROUP BY columnname);

delete from dept
where rowid in (
     select rowid
     from dept
     minus
     select max(rowid)
     from dept
     group by DEPTNO, DNAME, LOC
);

为了获得最佳性能，这是我写的内容：（
请参阅执行计划）

DELETE FROM your_table
WHERE rowid IN 
  (select t1.rowid from your_table  t1
      LEFT OUTER JOIN (
      SELECT MIN(rowid) as rowid, column1,column2, column3
      FROM your_table 
      GROUP BY column1, column2, column3
  )  co1 ON (t1.rowid = co1.rowid)
  WHERE co1.rowid IS NULL
);

检查以下脚本-

1。

Create table test(id int,sal int); 

2。

    insert into test values(1,100);    
    insert into test values(1,100);    
    insert into test values(2,200);    
    insert into test values(2,200);    
    insert into test values(3,300);    
    insert into test values(3,300);    
    commit;

3。

 select * from test;    

您将在这里看到6条记录。
4.运行以下查询-

delete from 
   test
where rowid in
 (select rowid from 
   (select 
     rowid,
     row_number()
    over 
     (partition by id order by sal) dup
    from test)
  where dup > 1)

5. select * from test;

您将看到重复的记录已被删除。
希望这可以解决您的查询。谢谢 ：）

我没有看到使用常用表表达式和窗口函数的任何答案。这是我发现最容易使用的方法。

DELETE FROM
 YourTable
WHERE
 ROWID IN
    (WITH Duplicates
          AS (SELECT
               ROWID RID, 
               ROW_NUMBER() 
               OVER(
               PARTITION BY First_Name, Last_Name, Birth_Date)
                  AS RN
               SUM(1)
               OVER(
               PARTITION BY First_Name, Last_Name, Birth_Date
               ORDER BY ROWID ROWS BETWEEN UNBOUNDED PRECEDING 
                                       AND UNBOUNDED FOLLOWING)
                   AS CNT
              FROM
               YourTable
              WHERE
               Load_Date IS NULL)
     SELECT
      RID
     FROM
      duplicates
     WHERE
      RN > 1);

注意事项：

1）我们只检查partition子句中的字段是否重复。

2）如果您出于某种原因要选择一个重复项，则可以使用order by子句使该行的row_number（）= 1

3）您可以通过将final where子句更改为“ Where RN> N”（其中N> = 1）来更改保留的重复数（我以为N = 0会删除所有重复的行，但只会删除所有行） 。

4）在“总和”分区字段中添加了CTE查询，该字段将使用组中的数字行标记每一行。因此，要选择包含重复项的行（包括第一项），请使用“ WHERE cnt> 1”。

create or replace procedure delete_duplicate_enq as
    cursor c1 is
    select *
    from enquiry;
begin
    for z in c1 loop
        delete enquiry
        where enquiry.enquiryno = z.enquiryno
        and rowid > any
        (select rowid
        from enquiry
        where enquiry.enquiryno = z.enquiryno);
    end loop;
 end delete_duplicate_enq;

解决方案：

delete from emp where rowid in
(
    select rid from
    (
        select rowid rid,
        row_number() over(partition by empno order by empno) rn
        from emp
    )
    where rn > 1
);