Create Partition in an Old Table Oracle

You can partition a non-partitioned table three different ways:

A) export/import method
B) Insert with a subquery method
C) Partition exchange method

Either of these 3 methods will create a partitioned table from an existing non-partitioned table.

A. Export/import method


1) Export your table:

exp usr/pswd tables=numbers file=exp.dmp

2) Drop the table:

drop table numbers;

3) Recreate the table with partitions:

create table numbers (qty number(3), name varchar2(15))
partition by range (qty)
(partition p1 values less than (501),
partition p2 values less than (maxvalue));

4) Import the table with ignore=y:

imp usr/pswd file=exp.dmp ignore=y

The ignore=y causes the import to skip the table creation and
continues to load all rows.

B. Insert with a subquery method


1) Create a partitioned table:

create table partbl (qty number(3), name varchar2(15))
partition by range (qty)
(partition p1 values less than (501),
partition p2 values less than (maxvalue));

2) Insert into the partitioned table with a subquery from the
non-partitioned table:

insert into partbl (qty, name)
select * from origtbl;

3) If you want the partitioned table to have the same name as the
original table, then drop the original table and rename the
new table:

drop table origtbl;
alter table partbl rename to origtbl;


C. Partition Exchange method

ALTER TABLE EXCHANGE PARTITION can be used to convert a partition (or subpartition) into a non-partitioned table and a non-partitioned table into a partition (or subpartition) of a partitioned table by exchanging their data and index segments.

1) Create table dummy_t as select with the required partitions
2) Alter table EXCHANGE partition with ;


Example
-------

SQL> CREATE TABLE p_emp
2 (sal NUMBER(7,2))
3 PARTITION BY RANGE(sal)
4 (partition emp_p1 VALUES LESS THAN (2000),
5 partition emp_p2 VALUES LESS THAN (4000));
Table created.


SQL> SELECT * FROM emp;
EMPNO ENAME JOB MGR HIREDATE SAL
--------- ---------- --------- --------- --------- ---------
7369 SMITH CLERK 7902 17-DEC-80 800
7499 ALLEN SALESMAN 7698 20-FEB-81 1600
7521 WARD SALESMAN 7698 22-FEB-81 1250
7566 JONES MANAGER 7839 02-APR-81 2975
7654 MARTIN SALESMAN 7698 28-SEP-81 1250
7698 BLAKE MANAGER 7839 01-MAY-81 2850
7782 CLARK MANAGER 7839 09-JUN-81 2450
7788 SCOTT ANALYST 7566 19-APR-87 3000
7839 KING PRESIDENT 17-NOV-81 5000
7844 TURNER SALESMAN 7698 08-SEP-81 1500
7876 ADAMS CLERK 7788 23-MAY-87 1100
7900 JAMES CLERK 7698 03-DEC-81 950
7902 FORD ANALYST 7566 03-DEC-81 3000
7934 MILLER CLERK 7782 23-JAN-82 1300
14 rows selected.

SQL> CREATE TABLE dummy_y as SELECT sal
FROM emp WHERE sal CREATE TABLE dummy_z as SELECT sal FROM emp WHERE sal
BETWEEN 2000 AND 3999;
Table created.

SQL> alter table p_emp exchange partition emp_p1
with table dummy_y;
Table altered.

SQL> alter table p_emp exchange partition emp_p2
with table dummy_z;
Table altered.


Another Detailed Example using Partition Exchange method


    -- Create and populate a small lookup table.
    CREATE TABLE lookup (
      id            NUMBER(10),
      description   VARCHAR2(50)
    );

    ALTER TABLE lookup ADD (
      CONSTRAINT lookup_pk PRIMARY KEY (id)
    );

    INSERT INTO lookup (id, description) VALUES (1, 'ONE');
    INSERT INTO lookup (id, description) VALUES (2, 'TWO');
    INSERT INTO lookup (id, description) VALUES (3, 'THREE');
    COMMIT;

    -- Create and populate a larger table that we will later partition.
    CREATE TABLE big_table (
      id            NUMBER(10),
      created_date  DATE,
      lookup_id     NUMBER(10),
      data          VARCHAR2(50)
    );

    DECLARE
      l_lookup_id    lookup.id%TYPE;
      l_create_date  DATE;
    BEGIN
      FOR i IN 1 .. 1000000 LOOP
        IF MOD(i, 3) = 0 THEN
          l_create_date := ADD_MONTHS(SYSDATE, -24);
          l_lookup_id   := 2;
        ELSIF MOD(i, 2) = 0 THEN
          l_create_date := ADD_MONTHS(SYSDATE, -12);
          l_lookup_id   := 1;
        ELSE
          l_create_date := SYSDATE;
          l_lookup_id   := 3;
        END IF;
        
        INSERT INTO big_table (id, created_date, lookup_id, data)
        VALUES (i, l_create_date, l_lookup_id, 'This is some data for ' || i);
      END LOOP;
      COMMIT;
    END;
    

    -- Apply some constraints to the table.
    ALTER TABLE big_table ADD (
      CONSTRAINT big_table_pk PRIMARY KEY (id)
    );

    CREATE INDEX bita_created_date_i ON big_table(created_date);

    CREATE INDEX bita_look_fk_i ON big_table(lookup_id);

    ALTER TABLE big_table ADD (
      CONSTRAINT bita_look_fk
      FOREIGN KEY (lookup_id)
      REFERENCES lookup(id)
    );

    -- Gather statistics on the schema objects
    EXEC DBMS_STATS.gather_table_stats(USER, 'LOOKUP', cascade => TRUE);
    EXEC DBMS_STATS.gather_table_stats(USER, 'BIG_TABLE', cascade => TRUE);


    -- Create partitioned table.
    CREATE TABLE big_table2 (
      id            NUMBER(10),
      created_date  DATE,
      lookup_id     NUMBER(10),
      data          VARCHAR2(50)
    )
    PARTITION BY RANGE (created_date)
    (PARTITION big_table_2007 VALUES LESS THAN (MAXVALUE));

    -- Add new keys, FKs and triggers.
    ALTER TABLE big_table2 ADD (
      CONSTRAINT big_table_pk2 PRIMARY KEY (id)
    );

    CREATE INDEX bita_created_date_i2 ON big_table2(created_date) LOCAL;

    CREATE INDEX bita_look_fk_i2 ON big_table2(lookup_id) LOCAL;

    ALTER TABLE big_table2 ADD (
      CONSTRAINT bita_look_fk2
      FOREIGN KEY (lookup_id)
      REFERENCES lookup(id)
    );


      ALTER TABLE big_table2
      EXCHANGE PARTITION big_table_2007
      WITH TABLE big_table
      WITHOUT VALIDATION
      UPDATE GLOBAL INDEXES;

    DROP TABLE big_table;
    RENAME big_table2 TO big_table;

    ALTER TABLE big_table RENAME CONSTRAINT big_table_pk2 TO big_table_pk;
    ALTER TABLE big_table RENAME CONSTRAINT bita_look_fk2 TO bita_look_fk;
    ALTER INDEX big_table_pk2 RENAME TO big_table_pk;
    ALTER INDEX bita_look_fk_i2 RENAME TO bita_look_fk_i;
    ALTER INDEX bita_created_date_i2 RENAME TO bita_created_date_i;

      ALTER TABLE big_table
      SPLIT PARTITION big_table_2007 AT (TO_DATE('31-DEC-2005 23:59:59', 'DD-MON-YYYY HH24:MI:SS'))
      INTO (PARTITION big_table_2005,
            PARTITION big_table_2007)
      UPDATE GLOBAL INDEXES;

      ALTER TABLE big_table
      SPLIT PARTITION big_table_2007 AT (TO_DATE('31-DEC-2006 23:59:59', 'DD-MON-YYYY HH24:MI:SS'))
      INTO (PARTITION big_table_2006,
            PARTITION big_table_2007)
      UPDATE GLOBAL INDEXES;

     EXEC DBMS_STATS.gather_table_stats(USER, 'BIG_TABLE', cascade => TRUE);


    SELECT partitioned
    FROM   user_tables
    WHERE  table_name = 'BIG_TABLE';

    PAR
    ---
    YES

    1 row selected.

    SELECT partition_name, num_rows
    FROM   user_tab_partitions
    WHERE  table_name = 'BIG_TABLE';

    PARTITION_NAME                   NUM_ROWS
    ------------------------------ ----------
    BIG_TABLE_2005                     335326
    BIG_TABLE_2006                     332730
    BIG_TABLE_2007                     334340

    3 rows selected.


Thanks
A Rahim Khan

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  1. January 10th, 2015
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