Merging Partitions
使用ALTER TABLE .. MERGE PARTITION语句将两个分区的内容合并到另外一个分区，两个源分区和关联的local index都会被drop
不能用于 hash分区表或 hash subpartitions of a composite *-hash partitioned table
不能用于合并引用分区表(reference-partitioned table)
合并范围分区
允许合并两个临近范围的分区到另外分区，不相邻分区无法合并。合并结果分区继承两个源分区的最大边界。
demo:
-- Create a Table with four partitions each on its own tablespace
-- Partitioned by range on the data column.
CREATE TABLE four_seasons
(
one DATE,
two VARCHAR2(60),
three NUMBER
)
PARTITION BY RANGE ( one )
(
PARTITION quarter_one
VALUES LESS THAN ( TO_DATE('01-apr-1998','dd-mon-yyyy'))
TABLESPACE quarter_one,
PARTITION quarter_two
VALUES LESS THAN ( TO_DATE('01-jul-1998','dd-mon-yyyy'))
TABLESPACE quarter_two,
PARTITION quarter_three
VALUES LESS THAN ( TO_DATE('01-oct-1998','dd-mon-yyyy'))
TABLESPACE quarter_three,
PARTITION quarter_four
VALUES LESS THAN ( TO_DATE('01-jan-1999','dd-mon-yyyy'))
TABLESPACE quarter_four
);
-- Create local PREFIXED index on Four_Seasons
-- Prefixed because the leftmost columns of the index match the
-- Partitioning key CREATE INDEX i_four_seasons_l ON four_seasons ( one,two )
LOCAL (
PARTITION i_quarter_one TABLESPACE i_quarter_one,
PARTITION i_quarter_two TABLESPACE i_quarter_two,
PARTITION i_quarter_three TABLESPACE i_quarter_three,
PARTITION i_quarter_four TABLESPACE i_quarter_four
);
下一步，合并分区.
-- Merge the first two partitions
--
ALTER TABLE four_seasons
MERGE PARTITIONS quarter_one, quarter_two INTO PARTITION quarter_two
UPDATE INDEXES;
如果不显式声明 UPDATE INDEXES 语句,就必须给受影响的分区 rebuild the local index.
-- Rebuild index for quarter_two, which has been marked unusable
-- because it has not had all of the data from Q1 added to it.
-- Rebuilding the index will correct this.
--
ALTER TABLE four_seasons MODIFY PARTITION
quarter_two REBUILD UNUSABLE LOCAL INDEXES;
合并Interval Partitions
同RANGE一样，必须两个相邻分区才能合并
合并 List partitions则没有限制