help，mysql存储过程问题

SQL code

CREATE DEFINER=`root`@`localhost` PROCEDURE `test`(
        IN id BIGINT(20),
        IN newSize int(20),
        IN newConut int(20),
        IN newPrice FLOAT(8,4)
    )
BEGIN
 DECLARE Size INT;
 DECLARE Count INT;
 DECLARE Price FLOAT;
set @q1=CONCAT('select size,count,price INTO Size,Count,Price from ',id,'_testschema.testtable where datetime BETWEEN "',CURDATE(),' 00:00:00" and "',CURDATE(),' 23:59:59"');
prepare st1 from @q1;
deallocate prepare st1;
..
..
..
..
end
[code=SQL]

[/code]
存储过程如上，主要是先定义三个变量，然后将sql语句用concat生成，由于需要操作的数据是在另一个数据库中的，故该存储过程还接收数据库名字作为参数，现在这样写之后提示我Size变量未定义

set @q1=CONCAT('select size,count,price INTO @Size,@Count,@Price from ',id,'_testschema.testtable where datetime BETWEEN "',CURDATE(),' 00:00:00" and "',CURDATE(),' 23:59:59"');
prepare st1 from @q1;
deallocate prepare st1;