drop function if exists _is_first_date;
DELIMITER //
create function _is_first_date ( _date varchar(8) )
returns boolean

begin
   declare ret boolean;
	   if substring(_date, 7,2) = '01' then
    	   set ret = true;
      else
    	   set ret = false;
      end if;
   return ret;
end; //
DELIMITER ;

select _is_first_date('20220101')