oracle删除重复数据

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create table test_0210(id number,name varchar2(32),age number);
insert into test_0210 values(1,'abc',32);
insert into test_0210 values(2,'def',33);
insert into test_0210 values(3,'def',45);
commit;

SQL> select * from test_0210;

        ID NAME                                    AGE
---------- -------------------------------- ----------
         1 abc                                      32
         2 def                                      33
         3 def                                      45

1.使用rowid 效率高直接定位到数据块地址,根据需要取max rowid 或 min rowid 只适合删除少量重复数据

SQL> delete from test_0210 where rowid not in (select max(rowid) from test_0210 group by name);

1 row deleted

SQL> select * from test_0210;

        ID NAME                                    AGE
---------- -------------------------------- ----------
         1 abc                                      32
         3 def                                      45

2.利用ID 只适合删除少量重复数据

SQL> delete from test_0210 where id not in (select max(id) from test_0210 group by name);

1 row deleted

SQL> select * from test_0210;

        ID NAME                                    AGE
---------- -------------------------------- ----------
         1 abc                                      32
         3 def                                      45

3.创建临时表 ,这种方法适合删除大量重复数据

SQL> create table test_temp as select * from test_0210 where id in (select max(id) from test_0210 group by name)
2 ;

Table created

SQL> truncate table test_0210;

Table truncated

SQL> insert into test_0210 select * from test_temp;

2 rows inserted

SQL> commit;

Commit complete

SQL> select * from test_0210;

        ID NAME                                    AGE
---------- -------------------------------- ----------
         1 abc                                      32
         3 def                                      45

4:也是创建临时表这里用的是分析函数

SQL> create table test_temp as select id,name,age from (select row_number() over(partition by name order by id) rn ,id,name,age
2                  from test_0210) where rn=1;

Table created

SQL> truncate table test_0210;

Table truncated

SQL> insert into test_0210 select * from test_temp;

2 rows inserted

SQL> commit;

Commit complete

SQL> select * from test_0210;

        ID NAME                                    AGE
---------- -------------------------------- ----------
         1 abc                                      32
         2 def                                      33

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