Generate Taiwan ID in PostgreSQL

fake_twid.sql

create or replace function fake_twid()
   returns text
   language plpgsql
  as
$$
declare 
	ret text;
	check_num int;
	check_index int[];
	digit int;
	i int;
begin
	check_index = '{10,11,12,13,14,15,16,17,34,18,19,20,21,22,35,23,24,25,26,27,28,29,32,30,31,33}';
	ret = chr(ascii('A')+floor(random()*26)::int+1);
	check_num = (check_index[ascii(ret)-ascii('A')+1]/10)::int+(check_index[ascii(ret)-ascii('A')+1]%10)*9;
	digit = floor(random()*2+1)::int;
	check_num = check_num + digit*8;
	ret = ret||digit;
	for i in 1..7 loop
		digit = floor(random()*10)::int;
		check_num = check_num+digit*(8-i);
		ret = ret||digit;
	end loop;
	check_num = check_num%10;
	if check_num>0 then
		check_num = 10-check_num;
	end if;
	ret = ret||check_num;
	return ret;
end;
$$;