create or replace function count_langs_employee(worker_name varchar)
return number
is
    counter number;
begin
    select count(language)
    into counter
    from table_A
    where ename = worker_name;

    return counter;
end;

CREATE or replace type native_speaker as object(
    i VARCHAR(50)
);

create or replace type native_speakers as TABLE of native_speaker;

create or replace function language_speakers(lang VARCHAR)
return native_speakers as all_speakers  native_speakers;
begin
    select native_speaker(ename)
    bulk collect into all_speakers
    from table_A
    where language = lang;

    return all_speakers;
end;

create or replace function best_speaker(lang varchar)
return varchar as best_speaker varchar(50);
begin
    select listagg(i, ' ')
    into best_speaker
    from TABLE(language_speakers(lang))
    where count_langs_employee(i) = (select max(count_langs_employee(i)) from table(language_speakers(lang)));

    return best_speaker;
end;

select language, best_speaker(language) from table_A
group by language
order by length(best_speaker(language))