多项选择题 You execute this command to drop the ITEM table， which has the primary key referred in the ORDERS table：SQL> DROP TABLE scott.item CASCADE CONSTRAINTS PURGE；  Which two statements are true about theeffect of the command（）

单项选择题 You want to import schema objects of the HR user using Oracle Data Pump from the development database，DEVDB， to the production database， PRODDB. A database link devdb.us.oracle.com is created betweenPRODDB and DEVDB. You execute the following command on the PRODDB database server：$ impdp system/manager directory = DB_DATAdumpfile = schemas.datschemas = hr flashback_time = "TO_TIMESTAMP（’25-08-2007 14：35：00’， ’DD-MM-YYYY HH24：MI：SS’）"The command fails displaying the following error：ORA-39001： invalid argument valueORA-39000： bad dump file specification ORA-31640： unable to open dump file "/home/oracle/schema/schemas.dat" for read ORA-27037： unable toobtain file status What would you do to overcome the error（）

多项选择题 Which two operations can be performed on an external table（）