Autoincrement Primary key in Oracle database
As Orbman says, the standard way to do it is with a sequence. What most people also do is couple this with an insert trigger. So, when a row is inserted without an ID, the trigger fires to fill out the ID for you from the sequence.
CREATE SEQUENCE SEQ_ROLLINGSTOCK_ID START WITH 1 INCREMENT BY 1 NOCYCLE;CREATE OR REPLACE TRIGGER BI_ROLLINGSTOCKBEFORE INSERT ON ROLLINGSTOCKREFERENCING OLD AS OLD NEW AS NEWFOR EACH ROW WHEN (NEW.ID IS NULL)BEGIN select SEQ_ROLLINGSTOCK_ID.NEXTVAL INTO :NEW.ID from dual;END;This is one of the few cases where it makes sense to use a trigger in Oracle.
If you really don't care what the primary key holds, you can use a RAW type for the primary key column which holds a system-generated guid in binary form.
CREATE TABLE RollingStock ( ID RAW(16) DEFAULT SYS_GUID() PRIMARY KEY, NAME VARCHAR2(80 CHAR) NOT NULL );