mysql数据库外键的使用，随主表同时更新或删除

Posted 2020-10-27 听风且雨

现在有一个图书表，记载了图书信息，图书id为nh_id，

要求有一个图书章节表，按章节记载图书的具体信息，外键nh_id对应图书表的nh_id，同时要求如果图书表id改变，对应的章节表的外键也改变，如果图书删除，该书对应的章节也一并删除

添加外键约束为

CONSTRAINT `nh_chapter-nh` FOREIGN KEY (`nh_id`) REFERENCES `nh` (`nh_id`) ON DELETE CASCADE ON UPDATE CASCADE

其中

CONSTRAINT `nh_chapter-nh` FOREIGN KEY (`nh_id`) REFERENCES `nh` (`nh_id`)

为建立外键

 

 

ON DELETE CASCADE ON UPDATE CASCADE

为一并删除或更新

 

 

完整参考

CREATE TABLE `nh` (
  `nh_id` int(10) unsigned NOT NULL AUTO_INCREMENT COMMENT ‘小说编号‘,
  `type` tinyint(2) unsigned NOT NULL COMMENT ‘类型‘,
  `sex` tinyint(1) unsigned NOT NULL COMMENT ‘性别[1男2女]‘,
  `name` varchar(100) NOT NULL COMMENT ‘名称‘,
  `intro` varchar(1500) NOT NULL COMMENT ‘简介‘,
  `words` varchar(10) NOT NULL COMMENT ‘字数‘,
  `author` varchar(30) NOT NULL COMMENT ‘作者‘,PRIMARY KEY (`nh_id`)
) ENGINE=InnoDB AUTO_INCREMENT=10613 DEFAULT CHARSET=utf8mb4 COMMENT=‘小说表‘;


CREATE TABLE `nh_chapter` (
  `chapter_id` int(10) unsigned NOT NULL AUTO_INCREMENT COMMENT ‘章节编号‘,
  `index` int(10) unsigned NOT NULL COMMENT ‘章节编号‘,
  `nh_id` int(10) unsigned NOT NULL COMMENT ‘小说编号‘,
  `title` varchar(100) NOT NULL COMMENT ‘标题‘,
  `total` int(10) unsigned NOT NULL COMMENT ‘章节字数‘,
  `content` mediumtext NOT NULL COMMENT ‘章节内容‘,
  PRIMARY KEY (`chapter_id`),KEY `nh_id` (`nh_id`),
  CONSTRAINT `nh_chapter-nh` FOREIGN KEY (`nh_id`) REFERENCES `nh` (`nh_id`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB AUTO_INCREMENT=244808 DEFAULT CHARSET=utf8mb4 COMMENT=‘小说章节表‘;