DECLARE 
  TYPE dnames_tab IS TABLE OF VARCHAR2(30); 
  
  dept_names dnames_tab := dnames_tab( 
    'Shipping','Sales','Finance','Payroll');  -- Initialized to non-null value 
  
  empty_set dnames_tab;  -- Not initialized, therefore null 
  
  PROCEDURE print_dept_names_status IS 
  BEGIN 
    IF dept_names IS NULL THEN 
      DBMS_OUTPUT.PUT_LINE('dept_names is null.'); 
    ELSE 
      DBMS_OUTPUT.PUT_LINE('dept_names is not null.'); 
    END IF; 
  END  print_dept_names_status; 
  
BEGIN 
  print_dept_names_status; 
  dept_names := empty_set;  -- Assign null collection to dept_names. 
  print_dept_names_status; 
  dept_names := dnames_tab ( 
    'Shipping','Sales','Finance','Payroll');  -- Re-initialize dept_names 
  print_dept_names_status; 
END;