Request execution order, dictionnary dynamic views, new database creation

Question

Hi,
Could you tell me, in which order this sql request is executed:
select pro_name from product where pro_price =(select max(pro_price) from product);
Is the sub-request executed first and the principal request executed once the sub request has sent its result or
-is the principal request executed first, waiting the sub-request result when its arrived to
=(select max(pro_price) from product);
Thanks a lot for your answer
Secondly can you tell me what means the option "management local" when you create the system, sysaux and undo datafiles, for example like this
datafile 'C:\ORADATA\DBPROD\Base\DBPROD_SYSTEM_01.dbf' size 300M autoextend ON next 10M maxsize 500M extent management local
To finish, what permit to créate the et catoctk.sql script when you create the data dictionnary.
Thanks a lot for your answer.
Nathalie

Answer 1

1) The order in which elements of a SQL statement are processed is completely up to the optimizer. Which means that it is subject to change over time. Today, the optimizer may choose to execute a query one way, tomorrow, it may choose a different order of operations.
Now, practically, it is almost certain that Oracle would choose to evaluate the maximum price first and then scan the product table for the products with that maximum price. But that's just because there aren't any other options that would seem appealing. If you added another condition, it might make sense to evaluate that condition first and then find the maximum price.
2) Extent management local means that you are creating a locally managed tablespace. Assuming you're using a vaguely recent version of Oracle, all tablespaces are locally managed. Old versions of Oracle used dictionary managed tablespaces which basically meant that tracking information about when extents were allocated was stored in the SYSTEM tablespace. This was occasionally a performance problem which is why Oracle moved that information into the tablespace.
3) I'm not sure what you're asking when you ask about a "permit to create the catoctk.sql script"
Justin