存储过程动态取值和赋值问题

begin

  /*基础变量声明*/

DECLARE u_id int;

DECLARE r_id int;

DECLARE t_year int;



DECLARE b_name varchar(255);

DECLARE b_baifen decimal(10,2);

DECLARE b_quan decimal(10,6);

DECLARE b_value int;

DECLARE b_min decimal(10,4);

DECLARE b_max decimal(10,4);

DECLARE b_column_name varchar(255);

DECLARE b_table_name varchar(255);

DECLARE b_column_value decimal(10,4);



DECLARE result decimal(10,6) default 0.000000;

DECLARE done int(10);

DECLARE cursor_name CURSOR FOR select bin_baifen,bin_quan,bin_value,min_value,max_value,bin_column_name,bin_table_name  from jbfx_yinsu where bin_name=bname;

DECLARE continue handler for not found set done=1;

open cursor_name;

 loop_label:LOOP

  		fetch cursor_name into b_baifen,b_quan,b_value,b_min,b_max,b_column_name,b_table_name;

  			if done =1 then

       				 leave loop_label;

  			else

  				set @str = concat('select ',b_column_name,' into b_column_value from ',b_table_name,' where wenjuan_id =',w_id,' and tijian_id = ',t_id);

				prepare stmt1 from @str;

				execute stmt1;

				deallocate prepare stmt1;

				if b_value != null then

				  if b_value = b_column_value then

				     set result = result+b_baifen*b_quan;

                                 end if;

                                elseif (b_min != null) AND (b_max != null) then

                                   if (b_column_value>= b_min) AND (b_column_value < b_max) then

                                         set result = result+b_baifen*b_quan;

				  end if;

                             end if;

 		            end if;

  END LOOP;

close cursor_name;

select result;

end