利用row_number over 函数删除重复记录

开窗函数

Oracle从8.1.6开始提供分析函数，分析函数用于计算基于组的某种聚合值，它和聚合函数的不同之处是：对于每个组返回多行，而聚合函数对于每个组只返回一行

SQL> create table a1(id int,flag1 char(10),flag2 char(10));

Table created.

SQL> select * from a1;

ID FLAG1 FLAG2

---------- ---------- ----------

1 a a1

1 a a2

1 b b1

1 b b2

SQL> delete from (select unique a.* from a1 a);

delete from (select unique a.* from a1 a)

*

ERROR at line 1:

ORA-01732: data manipulation operation not legal on this view

SQL> delete from (select * from (select unique a.* from a1 a));

delete from (select * from (select unique a.* from a1 a))

*

ERROR at line 1:

ORA-01752: cannot delete from view without exactly one key-preserved table

SQL> delete from (select * from a1 group by id,name);

delete from (select * from a1 group by id,name)

*

ERROR at line 1:

ORA-01732: data manipulation operation not legal on this view

SQL> select a.*,row_number() over(partition by id,flag1 order by id,flag1) as num from a1 a;

ID FLAG1 FLAG2 NUM

---------- ---------- ---------- ----------

1 a a1 1

1 a a2 2

1 b b1 1

1 b b2 2

SQL> delete from (select a.*,row_number() over(partition by id,flag1 order by id,flag1) as num from a1 a) where num>1;

delete from (select a.*,row_number() over(partition by id,flag1 order by id,flag1) as num from a1 a) where num>1

*

ERROR at line 1:

ORA-01732: data manipulation operation not legal on this view

SQL> (select a.*,

row_number() over(partition by id, flag1 order by id, flag1) as num

from a1 a) 2 3 ;

ID FLAG1 FLAG2 NUM

---------- ---------- ---------- ----------

1 a a1 1

1 a a2 2

1 b b1 1

1 b b2 2

SQL> delete from a1 where rowid in (select rowid

from (select a.*,

row_number() over(partition by id, flag1 order by id, flag1) as num

from a1 a)a

where num >= 2) 2 3 4 5

6 ;

2 rows deleted.

SQL> commit;

Commit complete.

SQL> select * from a1;

ID FLAG1 FLAG2

---------- ---------- ----------

1 a a1

1 b b1