8、【E-R图 实体、属性、关系】

 create database exam;
CREATE TABLE `exam`.`shiti` ( `id` INT NOT NULL AUTO_INCREMENT , `title` VARCHAR(200) CHARACTER SET utf8mb3 COLLATE utf8mb3_general_ci NOT NULL , `answerA` VARCHAR(50) NOT NULL , `answerB` VARCHAR(50) NOT NULL , `answerC` VARCHAR(50) NOT NULL , `answerD` VARCHAR(50) NOT NULL , `tureda` CHAR(2) NOT NULL , `score` FLOAT NOT NULL , PRIMARY KEY (`id`)) ENGINE = InnoDB;
CREATE TABLE `exam`.`result` ( `stuid` CHAR(8) NOT NULL , `classid` CHAR(7) NOT NULL , `shitiid` INT NOT NULL , `uanswer` CHAR(2) NOT NULL , `score` FLOAT NOT NULL , `indate` TIMESTAMP NOT NULL ) ENGINE = InnoDB;
INSERT INTO `shiti` (`id`, `title`, `answerA`, `answerB`, `answerC`, `answerD`, `trueda`, `score`) VALUES ('1', '第一题1+2等于', '4', '2', '1', '3', 'D', '3'), ('2', '第二题2+2等于', '1', '3', '2', '4', 'D', '2');
ALTER TABLE `result` CHANGE `indate` `indate` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP;