Oracle hash分区

1.创建表

create table t1  
(  
  id varchar2(10),
  name varchar2(20)
)  
partition by hash(id)  
(  
  partition p1,  
  partition p2,  
  partition p3  
);      

2.查看数据

insert into t1 values('p1',1);
insert into t1 values('p1',2);
insert into t1 values('p3',3);      

3.查看数据

SQL> select * from t1;

ID                             NAME
------------------------------ ------------------------------------------------------------
p1                             1
p1                             2
p3                             3

SQL> select * from t1 partition(p1);

ID                             NAME
------------------------------ ------------------------------------------------------------
p1                             1
p1                             2

SQL> select * from t1 partition(p2);

no rows selected

SQL> select * from t1 partition(p3);

ID                             NAME
------------------------------ ------------------------------------------------------------
p3                             3      

4.存储过程插入大量数据

declare
  i number;
  begin
  for i in 1..1000000 loop
   insert into t1 values(i,'name');
  end loop;
  commit;
  end;
  /      

5.查看每个分区的数据，可以看出，存在数据倾斜。​

SQL> select count(1) from t1 partition(p1);

  COUNT(1)
----------
    249867

SQL> select count(1) from t1 partition(p2);

  COUNT(1)
----------
    500616

SQL> select count(1) from t1 partition(p3);

  COUNT(1)
----------
    249517