Get object_id of Database Object

To get the object id of an object you can query user_objects. Note that object_name is case-sensitive.

SQL> select object_id from user_objects where object_name='sample';

no rows selected

SQL> select object_id from user_objects where object_name='SAMPLE';

OBJECT_ID
----------
53673

[OR]

You can query dba_objects. Note that owner name is case-sensitive
SQL> select object_id, object_name from dba_objects where owner='SCOTT';

OBJECT_ID OBJECT_NAME
---------- --------------------------------------------------------------------------
53930 MASTER
53931 MASTER_MNO_PK
53932 CHILD1
53933 BIN$HfQPV+0lQOWmj9HXRXQ01w==$0
53934 CHILD2
51250 PK_DEPT
51249 DEPT
51251 EMP
51252 PK_EMP
51253 BONUS
51254 SALGRADE

OBJECT_ID OBJECT_NAME
---------- --------------------------------------------------------------------------
53673 SAMPLE
53674 BIN$aSuwOl8AQFCCphpKWoCRkg==$0
53675 BIN$Acsdzvs0RMewwv6ntnvFxQ==$0
54148 TEST

15 rows selected.