Question

（我使用工作台）我有questions表id, user_id, text和表users表id, name

我需要联系这两张桌子！

我写下以下内容：

ALTER TABLE `mydb_development`.`questions`
ADD CONSTRAINT fk_QueUsers_1
FOREIGN KEY (`user_id`)
REFERENCES `mydb_development`.`users`(`id`);

但我明白了：

ERROR 1046: No database selected
SQL Statement:
ALTER TABLE  `questions` 
ADD FOREIGN KEY (`user_id`) REFERENCES `users`(`id`)

ERROR: Error when running failback script. Details follow.

ERROR 1046: No database selected
SQL Statement:
CREATE TABLE `questions` (
  `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `user_id` int(11) unsigned NOT NULL,
  `text` text NOT NULL,
  `security_token` varchar(40) NOT NULL,
  `created_at` datetime NOT NULL,
  `updated_at` datetime NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=373 DEFAULT CHARSET=utf8

ERROR 1046: No database selected
SQL Statement:
ALTER TABLE  `questions` 
ADD FOREIGN KEY (`user_id`) REFERENCES `users`(`id`)

ERROR: Error when running failback script. Details follow.

.....................

修改我试着这样做：

USE `mydb_development`;

ALTER TABLE  `mydb_development`.`questions`

ADD CONSTRAINT `fk_QueUsers_1`

FOREIGN KEY (`user_id`)

REFERENCES  `mydb_development`.`users`(`id`);

我收到错误：

Error Code: 1005
Can't create table 'survey_development.#sql-4ad_45' (errno: 150)

不明白：S

修改

我的用户表：

DROP TABLE IF EXISTS `mydb_development`.`users`;
CREATE TABLE  `mydb_development`.`users` (
  `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `name` varchar(255) NOT NULL,
  `email` varchar(255) NOT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `email` (`email`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=latin1;

Answer 1

这似乎是mysql bug：

阅读http://forums.mysql.com/read.php?22,19755,19755

尝试索引'user_id'并再次运行脚本。

Answer 2

输入：

use `mydb_development`;

将约束名称'user_id'更改为其他内容，例如'fk_user_id'

Answer 3

尝试选择您的数据库以查看它是否有任何区别

USE `mydb_development`;

Answer 4

首先，您要摆脱ERROR 1046: No database selected错误。

为此，请确保您：

选择包含USE mydb_development;
修改ALTER/CREATE语句以包含数据库。例如。 ALTER TABLE mydb_development.questions

mysql alter table FOREIGN KEY！

4 个答案: