ตรวจสอบ Stored Procedure ชื่อ get_serialnumber
begin   declare serial_exist int;   declare xserial_no  int;   if param1='' then      select 'test' into param1;   end if;    select count(serial_no) into serial_exist from serial where name = param1;   if serial_exist = 0 then   insert into serial (name,serial_no) values (param1,0);   end if;   update serial set serial_no = serial_no + 1 where name = param1;   select serial_no into xserial_no from serial where name = param1;   return xserial_no;  end