How to create function in MySQL

drop function if exists function_name ;
delimiter $$
CREATE FUNCTION function_name [ (parameter datatype [, parameter datatype]) ]
RETURNS return_datatype
BEGIN
    -- statements
END
$$
-- for use the function 
select function_name(parameter);

drop function if exists countscoll;
delimiter $$
CREATE FUNCTION countscoll( cit int ) 
returns int 
begin 
   declare tota int ;
   set tota = ( select count(*) from school 
   where city = cit );
   return tota ;
end
$$
delimiter ;
select countscoll("new york");