Question

如果我在InnoDB引擎上设计数据库并且我有3个表我无法删除，因为每个表都说“外键约束失败” - 这是否意味着设计错误了？

请参阅以下结构：

CREATE TABLE IF NOT EXISTS `account` (
  `account_id` smallint(5) unsigned NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`account_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1 ;


CREATE TABLE IF NOT EXISTS `identity` (
  `identity_id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `user_id` int(10) unsigned DEFAULT NULL,
  `account_id` smallint(5) unsigned DEFAULT NULL,
  PRIMARY KEY (`identity_id`),
  KEY `fk_details1` (`user_id`),
  KEY `fk_account1` (`account_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1 ;


CREATE TABLE IF NOT EXISTS `user` (
  `user_id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `login` varchar(64) NOT NULL DEFAULT '',
  `password` varchar(32) NOT NULL DEFAULT '',
  `default_identity_id` int(10) unsigned DEFAULT NULL,
  PRIMARY KEY (`user_id`),
  UNIQUE KEY `login_UNIQUE` (`login`),
  KEY `fk_identity1` (`default_identity_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1 ;

--
-- Constraints for table `identity`
--
ALTER TABLE `identity`
  ADD CONSTRAINT `fk_details1` FOREIGN KEY (`user_id`) REFERENCES `user` (`user_id`) ON DELETE CASCADE ON UPDATE CASCADE,
  ADD CONSTRAINT `fk_account1` FOREIGN KEY (`account_id`) REFERENCES `account` (`account_id`) ON DELETE CASCADE ON UPDATE CASCADE;

--
-- Constraints for table `user`
--
ALTER TABLE `user`
  ADD CONSTRAINT `fk_identity1` FOREIGN KEY (`default_identity_id`) REFERENCES `identity` (`identity_id`) ON DELETE CASCADE ON UPDATE CASCADE;

我怀疑问题出在default_identity_id上......我应该把它作为身份表的标志移动吗？

请指教！

Answer 1

由于ypercube没有创造答案我会。

MySQL Database design. Inserting rows in 1to1 tables

这回答了我的问题 - 它比仅仅指向彼此表格更好，更灵活。感谢。

循环外键约束失败mysql

1 个答案: