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当我尝试

drop tables users;

它显示错误：无法删除或更新父行：外键约束失败

这是我的表：

CREATE TABLE `events` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `title` varchar(128) NOT NULL,
  `users_id` int(11) NOT NULL,
  `capacity` int(64) NOT NULL,
  `event_date` datetime NOT NULL,
  `text` text CHARACTER SET utf8 COLLATE utf8_czech_ci,
  `last_edit` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  PRIMARY KEY (`id`),
  KEY `users_id` (`users_id`),
  CONSTRAINT `events_ibfk_5` FOREIGN KEY (`users_id`) REFERENCES `users` (`id`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=utf8;


CREATE TABLE `users` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `email` varchar(100) NOT NULL,
  `password` varchar(100) NOT NULL,
  `role` enum('admin','member','guest','registered') NOT NULL DEFAULT 'registered',
  PRIMARY KEY (`id`),
  UNIQUE KEY `email` (`email`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;


CREATE TABLE `users_data` (
  `id` int(120) NOT NULL AUTO_INCREMENT,
  `users_id` int(11) DEFAULT NULL,
  `name` varchar(50) NOT NULL,
  `username` varchar(50) NOT NULL,
  `phone_number` varchar(25) NOT NULL,
  PRIMARY KEY (`id`),
  KEY `users_id` (`users_id`),
  CONSTRAINT `users_data_ibfk_5` FOREIGN KEY (`users_id`) REFERENCES `users` (`id`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=utf8;


CREATE TABLE `user_matches` (
  `user_id` int(120) NOT NULL,
  `match_id` int(11) NOT NULL,
  KEY `user_id` (`user_id`),
  KEY `match_id` (`match_id`),
  CONSTRAINT `user_matches_ibfk_4` FOREIGN KEY (`user_id`) REFERENCES `users_data` (`id`) ON DELETE CASCADE ON UPDATE CASCADE,
  CONSTRAINT `user_matches_ibfk_5` FOREIGN KEY (`match_id`) REFERENCES `users` (`id`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

我想我做错了外键，但我不确定如何正确更改它。感谢您的任何建议。

4

1 回答 1

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当您提交drop table usersMySQL 检查是否违反参照完整性约束时，即将提交删除。此检查失败，因为您定义了以下约束events：

CONSTRAINTevents_ibfk_5 FOREIGN KEY (users_id users_id 不能) REFERENCES同时(在) ON DELETE CASCADE ON UPDATE CASCADE 表events上的users_id字段NULL。因此，在删除表时，将users_id设置为NULL在提交期间失败。解决此问题的一种可能方法是删除表上字段的NOT NULL约束。users_idevents

于 2018-02-07T23:32:24.560 回答