产生错误错误代码：1215。无法在 mysql 中添加外键约束

Question

我做了2个这样的表，

CREATE TABLE personal (
id INT(255) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
name VARCHAR(30) NOT NULL,
email VARCHAR(50),
created_at DATETIME);


CREATE TABLE personal_details (
id INT(255) UNSIGNED AUTO_INCREMENT PRIMARY KEY NOT NULL,
personal_id INT(255),
tittle VARCHAR(10) NOT NULL,
family_name VARCHAR(50) NOT NULL, 
given_name VARCHAR(50) NOT NULL,
place_of_birth VARCHAR(50) NOT NULL,
date_of_birth DATE NOT NULL,
gender VARCHAR(25) NOT NULL,
country_citizen VARCHAR(50) NOT NULL,
national_identity_number INT(50) NOT NULL,
passport_no INT(50) NOT NULL,
issue_date DATE NOT NULL,
expiry_date DATE NOT NULL,
FOREIGN KEY (personal_id) REFERENCES personal(id)
);

但它 returns 像这样的错误 Error Code: 1215. Cannot add foreign key constraint

即使很难，我已经从另一个问题中找到了这个解决方案

Answer 1

我对两个 CREATE 语句之间的 use scholarship_uiii 有点困惑。

但错误的原因是您的 personal_id 字段缺少 UNSIGNED。所以你的第二个 CREATE-statement 应该是：

CREATE TABLE personal_details (
id INT(255) UNSIGNED AUTO_INCREMENT PRIMARY KEY NOT NULL,
personal_id INT(255) UNSIGNED,
tittle VARCHAR(10) NOT NULL,
family_name VARCHAR(50) NOT NULL, 
given_name VARCHAR(50) NOT NULL,
place_of_birth VARCHAR(50) NOT NULL,
date_of_birth DATE NOT NULL,
gender VARCHAR(25) NOT NULL,
country_citizen VARCHAR(50) NOT NULL,
national_identity_number INT(50) NOT NULL,
passport_no INT(50) NOT NULL,
issue_date DATE NOT NULL,
expiry_date DATE NOT NULL,
FOREIGN KEY (personal_id) REFERENCES personal(id)
);

产生错误错误代码：1215。无法在 mysql 中添加外键约束

produce an error Error Code: 1215. Cannot add foreign key constraint in mysql

mysql