CREATE OR REPLACE PROCEDURE listing AS
  emp EMPLOYEES%ROWTYPE;
  CURSOR cur IS SELECT * FROM EMPLOYEES;
BEGIN
    OPEN cur;
    LOOP
        FETCH cur INTO emp;
        EXIT WHEN cur%NOTFOUND;
        DBMS_OUTPUT.PUT(emp.first_name || ' ' || emp.last_name || ' ');
        IF emp.commission_pct IS NULL THEN
          DBMS_OUTPUT.PUT_LINE('false');
        ELSE
          DBMS_OUTPUT.PUT_LINE('true');
        END IF;
    END LOOP;
    CLOSE cur;
END;