test the difference between "DEFAULT NULL" and "DEFAULT 0"

/*
intent: test the difference between "DEFAULT NULL" and "DEFAULT 0"
anthor: t0nsha(liaodunxia{at}gmail.com@20081219)
*/
DECLARE
    ln_dft_null NUMBER DEFAULT NULL;
    ln_dft_zero NUMBER DEFAULT 0;
BEGIN
    ln_dft_null := ln_dft_null + 1;
    dbms_output.put_line('ln_dft_null = ' || ln_dft_null);
    ln_dft_zero := ln_dft_zero + 1;
    dbms_output.put_line('ln_dft_zero = ' || ln_dft_zero);
END;
/*dbms_output:
ln_dft_null =
ln_dft_zero = 1
*/