Mysql触发器new和old无法作为关键字使用

[我永远喜欢Amicus]

代码如下
-------------------------------
CREATE TABLE student_info (
stu_no INT(11) NOT NULL AUTO_INCREMENT,
stu_name VARCHAR(255) DEFAULT NULL,
class int(5),
PRIMARY KEY (stu_no)
);
CREATE TABLE student_count (
student_count INT(11) DEFAULT 0,
student_class int(5)
);

DELIMITER $$
CREATE TRIGGER trigger_student_count_insert
AFTER INSERT
ON student_info FOR EACH ROW
BEGIN
SET @newclass=new.student_info.class;
UPDATE student_count SET student_count=student_count+1 WHERE student_class=0;
UPDATE student_count SET student_count=student_count+1
WHERE student_count.`student_class`=@newclass;
END;
$$
DELIMITER ;

[ACMAIN_CHM]

看一下MYSQL官方手册中的例子中是怎么使用NEW的。