How to Create Auto Increment Columns in Oracle

CREATE TABLE test_table
(
ID NUMBER NOT NULL,
ID_COMPANY VARCHAR2(20 BYTE)
)

Table created.

CREATE SEQUENCE test_sequence
START WITH 1
INCREMENT BY 1;

Sequence created.

CREATE OR REPLACE TRIGGER test_trigger
BEFORE INSERT
ON test_table
REFERENCING NEW AS NEW
FOR EACH ROW
BEGIN
SELECT test_sequence.nextval INTO :NEW.ID FROM dual;
END;
/

Trigger created.

Now, test adding sample data

SQL> INSERT INTO test (ID_COMPANY) VALUES ('ABC123');

1 row created.

ps : Oracle is sucks. MySQL is sexy!