Create a print_bool function to display the values of BOOLEAN.

CREATE FUNCTION print_bool (v IN BOOLEAN) 
  RETURN VARCHAR2 
IS 
  v_rtn VARCHAR2(10); 
BEGIN 
  CASE v 
  WHEN TRUE THEN 
    v_rtn := 'TRUE'; 
  WHEN FALSE THEN 
    v_rtn := 'FALSE'; 
  ELSE 
    v_rtn := 'NULL'; 
  END CASE; 
  RETURN v_rtn; 
END print_bool;

DECLARE 
TYPE t_aa 
IS 
  TABLE OF BOOLEAN INDEX BY pls_integer; 
  v_aa1 t_aa := t_aa(1=>FALSE, 
                     2=>TRUE, 
                     3=>NULL); 
BEGIN 
  DBMS_OUTPUT.PUT_LINE(print_bool(v_aa1(1))); 
  DBMS_OUTPUT.PUT_LINE(print_bool(v_aa1(2))); 
  DBMS_OUTPUT.PUT_LINE(print_bool(v_aa1(3))); 
END;