Question

我正在尝试在两个表之间创建关系。这是每个表和外键创建的查询，

CREATE TABLE IF NOT EXISTS `quotes` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `quote` text COLLATE utf8_unicode_ci NOT NULL,
  `author` int(11) NOT NULL,
  `topic` int(11) NOT NULL,
  `language` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
  `created_at` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
  `updated_at` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
  PRIMARY KEY (`id`),
  KEY `author` (`author`),
  KEY `topic` (`topic`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;


CREATE TABLE IF NOT EXISTS `authors` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `author` int(11) NOT NULL,
  `period` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
  `photo` text COLLATE utf8_unicode_ci NOT NULL,
  `references` text COLLATE utf8_unicode_ci NOT NULL,
  `created_at` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
  `updated_at` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
  PRIMARY KEY (`id`),
  KEY `author` (`author`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=1 ;

ALTER TABLE `quotes` ADD FOREIGN KEY ( `author` ) REFERENCES `mytestdb`.`authors` (
`id`
) ON DELETE RESTRICT ON UPDATE RESTRICT ;

但它抛出了以下错误，

Error creating foreign key on author (check data types)

我不确定这个错误是什么。对此的任何帮助将不胜感激。

Answer 1

数据类型和符号必须相同

int与unsigned int

不同

显示宽度无关

author是一个签名的int

id是无符号整数

来自manual page：

外键和引用键中的对应列必须有类似的数据类型。整数类型的大小和符号必须是相同。字符串类型的长度不必相同。对于非二进制（字符）字符串列，字符集和排序规则必须是一样的。

它们具有相同的大小（int）。它们的征兆不同。

显示宽度10和11无关。

演示

create table referenced
(   id int(11) primary key
);

create table referencing
(   id int primary key,
    author int(10) not null,
    CONSTRAINT fk_blah FOREIGN KEY (author) REFERENCES referenced(id)
);

没有问题

CREATE TABLE IF NOT EXISTS `quotes` (
  `id` int(10) NOT NULL AUTO_INCREMENT,
  `quote` text COLLATE utf8_unicode_ci NOT NULL,
  `author` int(11) NOT NULL,
  `topic` int(11) NOT NULL,
  `language` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
  `created_at` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
  `updated_at` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
  PRIMARY KEY (`id`),
  KEY `author` (`author`),
  KEY `topic` (`topic`)
) ENGINE=InnoDB;


CREATE TABLE IF NOT EXISTS `authors` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `author` int(11) NOT NULL,
  `period` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
  `photo` text COLLATE utf8_unicode_ci NOT NULL,
  `references` text COLLATE utf8_unicode_ci NOT NULL,
  `created_at` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
  `updated_at` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
  PRIMARY KEY (`id`),
  KEY `author` (`author`),
  CONSTRAINT fk_blah222 FOREIGN KEY (author) REFERENCES quotes(id)
) ENGINE=InnoDB;

没有问题

创建外键时出错（检查数据类型）

1 个答案:

演示