【oracle】分区表：range分区，list分区，hash分区

--(1.1)官方推荐超过2G的表，需要分区表；

--(1.2)表中含有历史数据，新的数据添加到最新的分区；例如11个月的数据只是读，最新1个月的数据为修改；需要用分区表；

--(1.3)oracle 10g支持1024K-1个分区；

--(2)分区表的优点

--2.1 可以对单独的分区进行备份和恢复

--2.2 分散IO

--(3)oracle 10g支持的分区

--范围分区range

--哈希分区hash

--列表分区list

--范围哈希复合分区range-hash

--范围列表复合分区range-list

--(4)range分区

create table rangetable(id number(9),time date) partition by range(time)

(

partition p1 values less than (to_date(‘2010-2-1‘,‘yyyy-mm-dd‘) ),

partition p2 values less than (to_date(‘2010-3-1‘,‘yyyy-mm-dd‘) ),

partition p3 values less than (to_date(‘2010-4-1‘,‘yyyy-mm-dd‘) ),

partition p4 values less than(maxvalue)

);

--查看分区表的基本信息

select * from user_part_tables;

select table_name,partitioning_type,partition_count

from user_part_tables where table_name=‘RANGETABLE‘;

--查看表的分区信息:分区名称，默认的extents个数

select * from user_tab_partitions where table_name=‘RANGETABLE‘;

select table_name,high_value,partition_name from user_tab_partitions

--拆分分区表：拆分maxvale/default分区表；

alter table rangetable split partition p4 at(to_date(‘2010-5-1‘,‘yyyy-mm-dd‘))

into (partition p5,partition p6)

alter table rangetable split partition p6 at(to_date(‘2010-7-1‘,‘yyyy-mm-dd‘))

into (partition p6,partition p7)

--插入数据

insert into rangetable values(1,to_date(‘2010-01-01‘,‘yyyy-mm-dd‘));

insert into rangetable values(1,to_date(‘2010-02-01‘,‘yyyy-mm-dd‘));

insert into rangetable values(3,to_date(‘2010-03-01‘,‘yyyy-mm-dd‘));

select * from rangetable;

--统计segments

select partition_name,count(*) from user_extents where segment_name=‘RANGETABLE‘ group by partition_name;

--(5)list分区

--list分区必须制定列值，列植必须明确；要创建default分区来存储不明确的值；

create table listtable

(

id number(10) not null,

areacode varchar2(20)

)

partition by list(areacode)

(

partition list_025 values(‘025‘),

partition list_035 values(‘035‘),

partition list_045 values(‘045‘),

partition list_055 values(‘055‘),

partition list_other values (default)

)

--插入数据

insert into listtable values(1,‘025‘);

insert into listtable values(2,‘035‘);

insert into listtable values(3,‘045‘);

insert into listtable values(4,‘055‘);

insert into listtable values(5,‘075‘);

--查看分区信息

select * from user_part_tables;

select * from listtable;

select * from user_tab_partitions where table_name=‘LISTTABLE‘;

--统计segments

select partition_name,count(*) from user_extents where segment_name=‘LISTTABLE‘ group by partition_name;

--(6)hash分区

create table hashtable

(

id number(9),

areacode varchar2(10)

)

partition by hash(areacode)

partitions 5;

--插入数据

insert into hashtable values(1,‘025‘);

insert into hashtable values(2,‘035‘);

insert into hashtable values(3,‘045‘);

insert into hashtable values(4,‘055‘);

insert into hashtable values(5,‘075‘);

commit;

--统计segments

select partition_name,count(*) from user_extents where segment_name=‘HASHTABLE‘ group by partition_name;

select * from dba_extents  where segment_name=‘HASHTABLE‘;