How to create a sequence and a trigger that will emulate "autonumber" in other RDBMS systems

If you have been working with other RDBMS systems, such as SQL Server from Microsoft, you may be used to a datatype called AUTONUMBER, which will automatically insert a freshly generated number and create a unique value in your table. Perfect for generation of primary key values.
In oracle, no such data type exist. To achieve the same functionality, you need to create two additional objects: a sequence and a trigger. The trigger will fire on certain events. The sequence will generate a new number. Here is a simple example on how to set it up.

CREATE TABLE ADDRESSES
(
 ADDRESS_ID NUMBER,
 EMLOYEE_ID NUMBER,
 STREET_ADDRESS VARCHAR2(40),
 STREET_ADDRESS2 VARCHAR2(40),
 CITY VARCHAR2 (30),
 STATE VARCHAR2(2),
 ZIP VARCHAR2(5),
 ZIP_PLUS VARCHAR2(4),
 COUNTRY VARCHAR2(20),
 CONSTRAINT PK_ADDRESSES PRIMARY KEY (ADDRESS_ID)-- "OUT-OF-LINE" CONSTRAINT CREATION
);

CREATE SEQUENCE ADDRESSES_SEQ
 START WITH 1
 INCREMENT BY 1
 MINVALUE 1
 MAXVALUE 1000000
 NOCACHE
 NOCYCLE
 NOORDER;

CREATE OR REPLACE TRIGGER ADDRESSES_TRG
BEFORE INSERT
ON ADDRESSES
FOR EACH ROW
WHEN (NEW.ADDRESS_ID IS NULL)
BEGIN
 SELECT ADDRESSES_SEQ.NEXTVAL
 INTO   :NEW.ADDRESS_ID
 FROM   DUAL;
END;
/