OBJECT_ID pseudocolumn returns the object identifier of a column of an object table or view. Oracle uses this pseudocolumn as the primary key of an object table.
OBJECT_ID is useful in
OF triggers on views and for identifying the ID of a substitutable row in an object table.
In earlier releases, this pseudocolumn was called
SYS_NC_OID$. That name is still supported for backward compatibility. However, Oracle recommends that you use the more intuitive name
Oracle Database Object-Relational Developer's Guide for examples of the use of this pseudocolumn