range,hash,list分区

A.创建range分区，一般用于日期化处理，range分区可以很好的管理基于日期来分区的数据
创建样本数据表
create table zhangxb (orderid number(10),name varchar2(10),ls_date date);
insert into zhangxb values (1,'ls1',to_date('1981-01-02','yyyy-mm-dd'));
insert into zhangxb values (1,'ls2',to_date('1998-01-03','yyyy-mm-dd'));
insert into zhangxb values (1,'ls3',to_date('1999-01-04','yyyy-mm-dd'));
insert into zhangxb values (1,'ls4',to_date('2000-01-05','yyyy-mm-dd'));
insert into zhangxb values (1,'ls5',to_date('2000-01-06','yyyy-mm-dd'));
insert into zhangxb values (1,'ls6',to_date('2001-01-07','yyyy-mm-dd'));
insert into zhangxb values (1,'ls7',to_date('2001-01-08','yyyy-mm-dd'));
insert into zhangxb values (1,'ls8',to_date('2002-01-09','yyyy-mm-dd'));
insert into zhangxb values (1,'ls9',to_date('2002-01-10','yyyy-mm-dd'));
insert into zhangxb values (1,'ls10',to_date('2011-01-11','yyyy-mm-dd'));
创建range分区表
create table zhangxb_part
partition by range (ls_date)
(
partition zhangxb_part_1999_1 values less than (to_date('1999-01-01','yyyy-mm-dd')) ,
partition zhangxb_part_2000_1 values less than (to_date('2000-01-01','yyyy-mm-dd')) ,
partition zhangxb_part_2001_1 values less than (to_date('2001-01-01','yyyy-mm-dd')) ,
partition zhangxb_part_2002_1 values less than (to_date('2002-01-01','yyyy-mm-dd')) ,
partition zhangxb_part_2003_1 values less than (to_date('2003-01-01','yyyy-mm-dd')) ,
partition other values less than (maxvalue)
)
as select * from zhangxb;
查看分区
select * from zhangxb_part partition (zhangxb_part_1999_1);
select * from zhangxb_part partition (zhangxb_part_2000_1);
select * from zhangxb_part partition (zhangxb_part_2001_1);
select * from zhangxb_part partition (zhangxb_part_2002_1);
select * from zhangxb_part partition (zhangxb_part_2003_1);
select * from zhangxb_part partition (other);

B.创建hash分区，利用hash函数打散某列使数据均匀分布，一般用于均衡I/O，缺点数据不容易管理，哈希分区不能DROP、SPLIT 以及MERGE分区
我们创建了拥有10个分区的哈希分区表“zhangxb_HASH”
LS@LEO> create table zhangxb_hash partition by hash(object_id) partitions 10 as select * from dba_objects;
hash分区所占用的区个数，看每个分区占用的个数都差不多，说明数据还是比较均匀分布的
缺点：hash列上数值不能有太多的重复值，否则会导致数据分布不均匀
select partition_name,count(*) from user_extents where segment_name='zhangxb_HASH' group by partition_name;
PARTITION_NAME                   COUNT(*)
------------------------------ ----------
SYS_P27                                 3
SYS_P26                                 3
SYS_P22                                 2
SYS_P28                                 3
SYS_P29                                 2
SYS_P21                                 2
SYS_P23                                 3
SYS_P25                                 3
SYS_P30                                 2
SYS_P24                                 3
select count(*) from zhangxb_hash;

COUNT(*)
----------
      9860

C.创建list分区，一般用于数据可枚举，有限个值，可以考虑列表分区，例如国家名字，按州来分区
创建list分区表，我们按国家来分别存放在不同的州，每个州是一个分区
create table zhangxb_list
(
city_id NUMBER(5),
city_name VARCHAR2(30),
city_state VARCHAR2(20),
city_amount NUMBER(10)
)
partition by list (city_name)
(
partition  asia VALUES('china','japan'),
partition  europe VALUES ('germany','italy'),
partition  africa VALUES('libya','brazil'),
partition  other  VALUES(DEFAULT)              --默认分区
);
插入数据
insert into zhangxb_list values(1,'china','asia',100);
insert into zhangxb_list values(2,'germany','europe',101);
insert into zhangxb_list values(3,'libya','africa',102);
insert into zhangxb_list values(4,'zhangxb_city','other',103);
查看数据
LS@LEO> select * from zhangxb_list;

   CITY_ID COUNTRY_NAME                   STATE                CITY_AMOUNT
---------- ------------------------------ -------------------- -----------
         1 china                                               asia                         100
         2 germany                                      europe                       101
         3 libya                                                 africa                       102
         4 zhangxb_city                                 other                        103

注:3个分区，没有好坏，只有合适不合适而已，要根据自己数据库的情况和业务分析选择