Trigger für insert und update

CREATE OR REPLACE TRIGGER tbiu_tabellenname
before insert or update on tabellenname
for each row
begin
  if inserting then
    if :new.id is null then
       select seq_tabellenname.nextval
         into :new.id
         from dual;
    end if;
    if :new.aend_dat is null then
        select sysdate, user
          into :new.aend_dat, :new.aend_user
          from dual;
    end if;
  elsif updating then
    select sysdate, user
      into :new.aend_dat, :new.aend_user
      from dual;
  end if;
end;