Oracle 12.2版本中，增加了大量的分区新特性，这其中包括：
以下介绍的三个特性同样是12.2新增的：
多列列表分区、外部表分区、维护过滤
而对于多列列表分区的支持，也是大家关注已久的特性，先看一下脚本（在 livesql.oracle.com 测试执行，推荐动手实践）：
CREATE TABLE dba_by_db_in_yhem
(dbalic NUMBER,
username VARCHAR2(20),
dbcat VARCHAR2(4),
region VARCHAR2(10)
)
PARTITION BY LIST (dbcat, region)
(
PARTITION north_part VALUES (('ORCL','BEIJING'), ('ORCL','TIANJIN')),
PARTITION south_part VALUES (('DB2','SHENZHEN'), ('DB2','GUANGZHOU')),
PARTITION west_part VALUES (('SQL','CHENGDU'),('ORCL','CHENGDU'),('DB2','KUNMING')),
PARTITION east_part VALUES ('ORCL','SHANGHAI'),
PARTITION rest VALUES (DEFAULT)
);
insert into dba_by_db_in_yhem values(1,'EYGLE','ORCL','BEIJING');
insert into dba_by_db_in_yhem values(2,'KAMUS','ORCL','BEIJING');
insert into dba_by_db_in_yhem values(3,'LAOXIONG','SQL','CHENGDU');
insert into dba_by_db_in_yhem values(4,'ORA-600','DB2','GUANGZHOU');
insert into dba_by_db_in_yhem values(5,'YANGTINGKUN','ALL','BEIJING');
select * from dba_by_db_in_yhem partition (north_part);
select * from dba_by_db_in_yhem partition (south_part);
select * from dba_by_db_in_yhem partition (west_part);
select * from dba_by_db_in_yhem partition (east_part);
select * from dba_by_db_in_yhem partition (rest);
现在Oracle支持通过多列定义列表分区，最多支持16个列值定义，这极大的丰富了列表分区的适用场景。
为了简化维护操作，12.2 增加了维护过滤特性 - Filtered Partition on Maintenance Operations，也就是说，在执行分区的Move、Split和Merge等操作时，可以选择对数据进行过滤，通过一个 INCLUDING ROWS 进行限制。
继续前面的测试用例，当MOVE时指定保留分区中区域为「BEIJING」的数据后，『TIANJIN』的数据则被移除了：
insert into dba_by_db_in_yhem values(6,'SECOOLER','ORCL','TIANJIN');
select * from dba_by_db_in_yhem partition (north_part);
ALTER TABLE dba_by_db_in_yhem MOVE PARTITION north_part
INCLUDING ROWS WHERE REGION = 'BEIJING';
select * from dba_by_db_in_yhem partition (north_part);
在12.2中，Oracle还支持外部表分区，类似如下的语法展示了这一特性的用途，对于一个统一的外部表，可以通过分区指向不同的外部文件，不同文件可以用于存储已经分类的数据，从而更加灵活的使用外部表：
CREATE TABLE sales (loc_id number, prod_id number, cust_id number, amount_sold number, quantity_sold number)
ORGANIZATION EXTERNAL
(TYPE oracle_loader
DEFAULT DIRECTORY load_d1
ACCESS PARAMETERS
( RECORDS DELIMITED BY NEWLINE CHARACTERSET US7ASCII
NOBADFILE
LOGFILE log_dir:'sales.log'
FIELDS TERMINATED BY ","
)
)
REJECT LIMIT UNLIMITED
PARTITION BY RANGE (loc_id)
(PARTITION p1 VALUES LESS THAN (1000) LOCATION ('california.txt'),
PARTITION p2 VALUES LESS THAN (2000) DEFAULT DIRECTORY load_d2 LOCATION ('washington.txt'),
PARTITION p3 VALUES LESS THAN (3000))
;
了解了Oracle这些新的变化，将有助于我们深入和灵活的去使用Oracle数据库。
文章转自数据和云公众号，原文链接