ORA 2266 -- Drop parent partition with no child records exists

Question

Hi Team ,
Here I have a parent partitioned table and child refrenced non-partition table .
To drop parent partition I am doing
1)delete from child
2)delete from parent partition
3)alter table drop parent partition
---and its working fine .
I am trying to do below which is not working , Could you please guide me why it is not
1)delete from child
2)alter table drop parent partition -- throwing below error
Summarizing ,
Why I am not able to drop/trunc a parent partition(no corresponding rows exists in child tables) where as able to do after deleting the rows from parent partition .
From Doc :
Error: ORA 2266
Text: table has some unique/primary keys that are referenced by some foreign k
eys
Cause: Attempt to drop the table while the table still has some unique/
primary keys that are referenced by some foreign keys.
Action: Remove all such references to the keys before dropping the table
Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production
PL/SQL Release 11.2.0.2.0 - Production
CORE     11.2.0.2.0     Production
TNS for Linux: Version 11.2.0.2.0 - Production
NLSRTL Version 11.2.0.2.0 - Production

Answer 1

Oracle decides what the rules are & you must conform to them
bcm@bcm-laptop:~$ oerr ora 2266
02266, 00000, "unique/primary keys in table referenced by enabled foreign keys"
// *Cause: An attempt was made to truncate a table with unique or
//         primary keys referenced by foreign keys enabled in another table.
//         Other operations not allowed are dropping/truncating a partition of a
//         partitioned table or an ALTER TABLE EXCHANGE PARTITION.
// *Action: Before performing the above operations the table, disable the
//          foreign key constraints in other tables. You can see what
//          constraints are referencing a table by issuing the following
//          command:
//          SELECT * FROM USER_CONSTRAINTS WHERE TABLE_NAME = "tabnam";