create function NormalizePhoneNumbers (number TEXT)
returns text
deterministic
begin
	set @result := ',';
insert into trace values (1, @result);
	set number := trim(number);
insert into trace values (2, number);
	while number != '' do
		set @char := left(number, 1);
insert into trace values (3, @char);
		if locate(@char, '01023456789,') then
			set @result := concat(@result, @char);
insert into trace values (4, @result);
		end if;
		set number := trim(substring(number from 2));
insert into trace values (5, number);
	end while;
	return substring(replace(@result, ',8', ',+7') from 2);
end;

CREATE TABLE trace( number INT,  value TEXT );