ASELECT last_name, (salary * 12) * commission_pct FROM EMPLOYEES;
BSELECT last_name, (salary * 12) * IFNULL(commission_pct, 0) FROM EMPLOYEES;
CSELECT last_name, (salary * 12) * NVL2(commission_pct, 0) FROM EMPLOYEES;
DSELECT last_name, (salary * 12) * NVL(commission_pct, 0) FROM EMPLOYEES;