delimiter //

create or replace function format_iban(p_iban varchar(34)) returns varchar(34)
begin
    declare v_country varchar(2);
    declare v_part1 varchar(4);
    declare v_part2 varchar(4);
    declare v_part3 varchar(4);
    declare v_part4 varchar(4);
    declare v_part5 varchar(4);
    declare v_part6 varchar(2);
    declare v_result varchar(34);

    set v_country = substring(p_iban from 1 for 2);

    if (v_country = 'DE') then
        set v_part1 = substring(p_iban from 3 for 2);
        set v_part2 = substring(p_iban from 5 for 4);
        set v_part3 = substring(p_iban from 9 for 4);
        set v_part4 = substring(p_iban from 13 for 4);
        set v_part5 = substring(p_iban from 17 for 4);
        set v_part6 = substring(p_iban from 21 for 2);
        set v_result = concat(v_country, ' ', v_part1, ' ', v_part2, ' ', v_part3, ' ',
                              v_part4, ' ', v_part5, ' ', v_part6);
    else
        set v_result = p_iban;
    end if;

    return v_result;
end;
//

delimiter ;