Query to Partitioned Table

Question

I have two partition
upto_mar_2011 , upto_jun_2011
table_name : order
1> if I run query as below
Select * from order where order_date =to_date('23/03/2011','dd/mm/yyyy');
Oracle will automatically search the data in Partition upto_mar_2011
or it will search the data in whole table .
2> Or I have to give query as below
Select * from order partition (upto_mar_2011) where order_date =to_date('23/03/2011','dd/mm/yyyy');
Is there any difference between this two query

Answer 1

OraFighter wrote:
Is it enough to write as below
Select * from order where order_date = to_date('23/03/2011','dd/mm/yyyy')
or order_date = to_date(('23/05/2011','dd/mm/yyyy');
and CBO will search the data only the partition where it is available.
Wheather it is span in one or two or three partition
it will ignore all other partition automaticallyCorrect. It is called partition pruning. This is the approach you should use for application code. Applications should not be concerned with partitioning - should not need to know partition names and other physical attributes of the physical table it is using.
You can also see partition pruning when looking at the execution plan of such a SQL statement.
The only code that will deal with partition names and the physical aspects of the table, is maintenance code. For example, you need to maintain a sliding window of 32 days in the date ranged partitioned table. This code needs to determine which partitions are older than 32 days and drop them. And then add new partitions for future processing. This code deals with the physical layer and not the logical layer.
It is important to keep the two apart and not mix physical stuff into the logical layer that the app is using. Mixing it means that changes to optimise performance and leverage new features cannot be made to the physical layer, as it will break the app layer code.