1 环境 (1) 数据库 CREATE TABLE `t_student` ( `n_id` int(11) NOT NULL AUTO_INCREMENT, `c_name` varchar(255) DEFAULT NULL, `c_age` int(12) DEFAULT NULL, PRIMARY KEY (`n_id`) USING BTREE ) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8; CREATE TABLE `t_teacher` ( `n_id` int(11) NOT NULL AU