copying data from partition and converting

[PAVB]

I am looking to copy data from one partition to another for testing purposes.

My table is partitioned on create_date so I would like convert the old
create_date values (2011-05-20) to a new values (2011-05-21) so it
goes into another parition.

A simple insert statement will do it, be sure you populate your insert statement - probably with an append hint - from souce partition, like FROM mytable PARTITION (mysourcepartition)

In regards to adding one day to the date you can always use (mydate + 1) syntax.

I want is there any easy way to
convert null values to a default value.

Research NVL() function, like nvl(mycolumn, defaul-value)