There are a number of ways using SQL statements to modify
partitioned tables; it is possible to add, drop, redefine, merge,
or split existing partitions using the partitioning extensions to
the
ALTER
TABLE
statement. There are also ways to obtain
information about partitioned tables and partitions. We discuss
these topics in the sections that follow.
For information about partition management in tables partitioned by
RANGE
orLIST
, see Section 26.3.1, “Management of RANGE and LIST Partitions”.For a discussion of managing
HASH
andKEY
partitions, see Section 26.3.2, “Management of HASH and KEY Partitions”.See Section 26.3.5, “Obtaining Information About Partitions”, for a discussion of mechanisms provided in MySQL 8.4 for obtaining information about partitioned tables and partitions.
For a discussion of performing maintenance operations on partitions, see Section 26.3.4, “Maintenance of Partitions”.
All partitions of a partitioned table must have the same number of subpartitions; it is not possible to change the subpartitioning once the table has been created.
To change a table's partitioning scheme, it is necessary only
to use the
ALTER
TABLE
statement with a
partition_options
option, which has the
same syntax as that as used with CREATE
TABLE
for creating a partitioned table; this option
(also) always begins with the keywords PARTITION
BY
. Suppose that the following
CREATE TABLE
statement was used to
create a table that is partitioned by range:
CREATE TABLE trb3 (id INT, name VARCHAR(50), purchased DATE)
PARTITION BY RANGE( YEAR(purchased) ) (
PARTITION p0 VALUES LESS THAN (1990),
PARTITION p1 VALUES LESS THAN (1995),
PARTITION p2 VALUES LESS THAN (2000),
PARTITION p3 VALUES LESS THAN (2005)
);
To repartition this table so that it is partitioned by key into
two partitions using the id
column value as the
basis for the key, you can use this statement:
ALTER TABLE trb3 PARTITION BY KEY(id) PARTITIONS 2;
This has the same effect on the structure of the table as dropping
the table and re-creating it using CREATE TABLE trb3
PARTITION BY KEY(id) PARTITIONS 2;
.
ALTER TABLE ... ENGINE [=] ...
changes only the
storage engine used by the table, and leaves the table's
partitioning scheme intact. The statement succeeds only if the
target storage engine provides partitioning support. You can use
ALTER TABLE ... REMOVE PARTITIONING
to remove a
table's partitioning; see Section 15.1.9, “ALTER TABLE Statement”.
Only a single PARTITION BY
, ADD
PARTITION
, DROP PARTITION
,
REORGANIZE PARTITION
, or COALESCE
PARTITION
clause can be used in a given
ALTER
TABLE
statement. If you (for example) wish to drop a
partition and reorganize a table's remaining partitions,
you must do so in two separate
ALTER
TABLE
statements (one using DROP
PARTITION
and then a second one using
REORGANIZE PARTITION
).
You can delete all rows from one or more selected partitions using
ALTER TABLE ...
TRUNCATE PARTITION
.