产生一个错误错误码:1215.不能在mysql中添加外键约束

Question

我做了两个这样的表，

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)
);

但是它返回了这样的错误Error Code: 1215. Cannot add foreign key constraint

即使我已经从另一个问题中得到了这个解决方案

https://stackoverflow.com/a/16969116/17067132

Answer 1

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

但是错误的原因是您缺少personal_id字段的UNSIGNED。所以你的第二个CREATE语句应该是:

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)
);