2019-10-12 10:17:44
1、数据，建表时有可能会报错，只需要把前三行注释删掉就行
-- ---------------------------- -- Table structure for tb_grade -- ---------------------------- DROP TABLE IF EXISTS `tb_grade`; CREATE TABLE `tb_grade` ( `grade_id` int(11) NOT NULL AUTO_INCREMENT, `grade_name` varchar(50) DEFAULT NULL, PRIMARY KEY (`grade_id`), UNIQUE KEY `grade_check` (`grade_name`) USING BTREE ) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8; -- ---------------------------- -- Records of tb_grade -- ---------------------------- INSERT INTO `tb_grade` VALUES ('1', '一年级'); INSERT INTO `tb_grade` VALUES ('2', '二年级'); INSERT INTO `tb_grade` VALUES ('3', '三年级'); INSERT INTO `tb_grade` VALUES ('4', '四年级'); INSERT INTO `tb_grade` VALUES ('5', '五年级'); -- ---------------------------- -- Table structure for tb_subject -- ---------------------------- DROP TABLE IF EXISTS `tb_subject`; CREATE TABLE `tb_subject` ( `subject_id` int(11) NOT NULL AUTO_INCREMENT, `subject_name` varchar(20) DEFAULT NULL, `class_hour` int(3) DEFAULT NULL, `grade_id` int(11) DEFAULT NULL, PRIMARY KEY (`subject_id`), KEY `grade_id` (`grade_id`), CONSTRAINT `tb_subject_ibfk_1` FOREIGN KEY (`grade_id`) REFERENCES `tb_grade` (`grade_id`) ) ENGINE=InnoDB AUTO_INCREMENT=11 DEFAULT CHARSET=utf8; -- ---------------------------- -- Records of tb_subject -- ---------------------------- INSERT INTO `tb_subject` VALUES ('1', 'java', '60', '1'); INSERT INTO `tb_subject` VALUES ('2', 'html', '40', '1'); INSERT INTO `tb_subject` VALUES ('3', 'javascript', '30', '1'); INSERT INTO `tb_subject` VALUES ('4', 'database', '60', '2'); INSERT INTO `tb_subject` VALUES ('5', 'java oop', '60', '2'); INSERT INTO `tb_subject` VALUES ('6', 'servlet', '40', '2'); INSERT INTO `tb_subject` VALUES ('7', 'jsp', '40', '2'); INSERT INTO `tb_subject` VALUES ('8', 'struts2', '60', '3'); INSERT INTO `tb_subject` VALUES ('9', 'hibernate', '60', '3'); INSERT INTO `tb_subject` VALUES ('10', 'spring', '60', '3'); -- ---------------------------- -- Table structure for tb_student -- ---------------------------- DROP TABLE IF EXISTS `tb_student`; CREATE TABLE `tb_student` ( `student_no` varchar(20) NOT NULL COMMENT '学号', `login_pwd` varchar(20) NOT NULL DEFAULT '123456' COMMENT '密码', `student_name` varchar(20) NOT NULL COMMENT '姓名', `sex` enum('女','男') DEFAULT '男' COMMENT '性别', `grade_id` int(11) DEFAULT NULL COMMENT '年级 - 外键', `phone` varchar(20) DEFAULT NULL COMMENT '联系电话', `address` varchar(100) DEFAULT '学生宿舍' COMMENT '现住址', `birthday` date DEFAULT NULL COMMENT '出生日期', `email` varchar(50) DEFAULT NULL COMMENT '电子邮件', PRIMARY KEY (`student_no`), KEY `grade_id` (`grade_id`), CONSTRAINT `tb_student_ibfk_1` FOREIGN KEY (`grade_id`) REFERENCES `tb_grade` (`grade_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; -- ---------------------------- -- Records of tb_student -- ---------------------------- INSERT INTO `tb_student` VALUES ('s01', '123456', '宋江', '男', '1', '13888811111', '学生宿舍', '1985-10-10', '13888811111@qq.com'); INSERT INTO `tb_student` VALUES ('s02', '123456', '卢俊义', '男', '1', '13888822222', '教场西路8号', '1987-08-08', '13888822222@qq.com'); INSERT INTO `tb_student` VALUES ('s03', '123456', '吴用', '男', '2', '13888833333', '教场西路8号', '1991-06-06', '13888833333@qq.com'); INSERT INTO `tb_student` VALUES ('s04', '123456', '孙二娘', '女', '2', '13888844444', '教场西路16号', '1983-05-05', '13888844444@qq.com'); INSERT INTO `tb_student` VALUES ('s05', '123456', '李逵', '男', '1', '13888855555', '学生宿舍', '1992-01-01', '13888855555@qq.com'); INSERT INTO `tb_student` VALUES ('s06', '123456', '顾大嫂', '女', '1', '13888866666', '教场西路16号', '1990-02-02', '13888866666@qq.com'); INSERT INTO `tb_student` VALUES ('s07', '123456', '柴进', '男', '3', '13888877777', '学生宿舍', '1991-03-03', null); INSERT INTO `tb_student` VALUES ('s08', '123456', '林冲', '男', '3', '13888888888', '教场西路8号', '1986-04-04', null); INSERT INTO `tb_student` VALUES ('s09', '123456', '鲁智深', '男', '3', '13888899999', '教场西路8号', '1991-05-05', ''); INSERT INTO `tb_student` VALUES ('s10', '123456', '扈三娘', '女', '2', '13888800000', '学生宿舍', '1983-06-06', ''); -- ---------------------------- -- Table structure for tb_score -- ---------------------------- DROP TABLE IF EXISTS `tb_score`; CREATE TABLE `tb_score` ( `id` int(11) NOT NULL AUTO_INCREMENT COMMENT '成绩编号', `student_no` varchar(255) NOT NULL COMMENT '学号 - 外键', `subject_id` int(11) DEFAULT NULL COMMENT '所考科目', `student_score` float(5,2) DEFAULT '0.00' COMMENT '分数', `exam_date` date DEFAULT NULL COMMENT '考试日期', PRIMARY KEY (`id`), KEY `student_no` (`student_no`), KEY `subject_id` (`subject_id`), CONSTRAINT `tb_score_ibfk_1` FOREIGN KEY (`student_no`) REFERENCES `tb_student` (`student_no`), CONSTRAINT `tb_score_ibfk_2` FOREIGN KEY (`subject_id`) REFERENCES `tb_subject` (`subject_id`) ) ENGINE=InnoDB AUTO_INCREMENT=31 DEFAULT CHARSET=utf8; -- ---------------------------- -- Records of tb_score -- ---------------------------- INSERT INTO `tb_score` VALUES ('1', 's01', '1', '90.50', '2016-11-05'); INSERT INTO `tb_score` VALUES ('2', 's02', '1', '85.00', '2016-11-05'); INSERT INTO `tb_score` VALUES ('3', 's03', '1', '69.50', '2016-11-05'); INSERT INTO `tb_score` VALUES ('4', 's04', '1', '85.50', '2016-11-05'); INSERT INTO `tb_score` VALUES ('5', 's05', '1', '45.50', '2016-11-05'); INSERT INTO `tb_score` VALUES ('6', 's06', '1', '95.50', '2016-11-05'); INSERT INTO `tb_score` VALUES ('7', 's07', '1', '76.50', '2016-11-05'); INSERT INTO `tb_score` VALUES ('8', 's08', '1', '88.00', '2016-11-05'); INSERT INTO `tb_score` VALUES ('9', 's09', '1', '70.00', '2016-11-05'); INSERT INTO `tb_score` VALUES ('10', 's10', '1', '55.00', '2016-11-05'); INSERT INTO `tb_score` VALUES ('11', 's01', '2', '80.50', '2016-11-07'); INSERT INTO `tb_score` VALUES ('12', 's02', '2', '70.00', '2016-11-07'); INSERT INTO `tb_score` VALUES ('13', 's03', '2', '68.50', '2016-11-07'); INSERT INTO `tb_score` VALUES ('14', 's04', '2', '82.50', '2016-11-07'); INSERT INTO `tb_score` VALUES ('15', 's05', '2', '43.50', '2016-11-07'); INSERT INTO `tb_score` VALUES ('16', 's06', '2', '90.50', '2016-11-07'); INSERT INTO `tb_score` VALUES ('17', 's07', '2', '70.50', '2016-11-07'); INSERT INTO `tb_score` VALUES ('18', 's08', '2', '80.00', '2016-11-07'); INSERT INTO `tb_score` VALUES ('19', 's09', '2', '80.00', '2016-11-07'); INSERT INTO `tb_score` VALUES ('20', 's10', '2', '56.00', '2016-11-07'); INSERT INTO `tb_score` VALUES ('21', 's01', '3', '84.50', '2016-11-09'); INSERT INTO `tb_score` VALUES ('22', 's02', '3', '73.00', '2016-11-09'); INSERT INTO `tb_score` VALUES ('23', 's03', '3', '69.50', '2016-11-09'); INSERT INTO `tb_score` VALUES ('24', 's04', '3', '86.50', '2016-11-09'); INSERT INTO `tb_score` VALUES ('25', 's05', '3', '44.50', '2016-11-09'); INSERT INTO `tb_score` VALUES ('26', 's06', '3', '80.50', '2016-11-09'); INSERT INTO `tb_score` VALUES ('27', 's07', '3', '75.50', '2016-11-09'); INSERT INTO `tb_score` VALUES ('28', 's08', '3', '87.00', '2016-11-09'); INSERT INTO `tb_score` VALUES ('29', 's09', '3', '85.00', '2016-11-09'); INSERT INTO `tb_score` VALUES ('30', 's10', '3', '66.00', '2016-11-09');
2、表结构
3、需求：针对数据库中的4张数据表(tb_grade、tb_subject、tb_student、tb_score)
在需要的数据表上创建触发器，达到每删除一个数据表的记录时都能顺顺利执行(级联删除)。
4、具体实现：
-- 为tb_grade创建触发器 DROP TRIGGER IF EXISTS trig_grade; delimiter // CREATE TRIGGER trig_grade BEFORE delete on tb_grade for each row BEGIN DELETE FROM tb_student WHERE grade_id = old.grade_id; DELETE FROM tb_subject WHERE grade_id = old.grade_id; END // delimiter ; -- 为tb_student创建触发器 DROP TRIGGER IF EXISTS trig_student; delimiter // CREATE TRIGGER trig_student BEFORE delete on tb_student for each row BEGIN DELETE FROM tb_score WHERE student_no = old.student_no; END // delimiter ; -- 为tb_subject创建触发器 DROP TRIGGER IF EXISTS trig_subject; delimiter // CREATE TRIGGER trig_subject BEFORE delete on tb_subject for each row BEGIN DELETE FROM tb_score WHERE subject_id = old.subject_id; END // delimiter ; -- 查看此数据库中的触发器 SHOW TRIGGERS; -- 测试删除数据是否能成功 DELETE FROM tb_student WHERE student_no = "S01"; DELETE FROM tb_grade WHERE grade_id = 1; DELETE FROM tb_subject WHERE subject_id = 3; DELETE FROM tb_score WHERE id = 9;
-- 最后可以查询表看看有没有被顺利删除
5、tb_score表是没有其他表将外键指向它的主键
想要删除从表的数据，需要先删除主表的数据