Create AutoIncrement Field Oracle lower 12g

autoincrement.oracle.sql

-- Create Sequence
CREATE SEQUENCE USU_seq;
-- Create Trigger to manage fake autoincrement
CREATE OR REPLACE TRIGGER usu_bir  
BEFORE INSERT ON geo_usuarios 
FOR EACH ROW

BEGIN
  -- select next index from our sequence
  SELECT usu_seq.NEXTVAL
  -- chose autoincremental field (Warning: Verify your field name)
  INTO   :new.idusuario
  FROM   dual;
END;

--Select your current sequence index (At least used 1 time)
--SELECT usu_seq.CURRVAL from dual;