在 MySQL 中更改表时出错

Question

我编写了一个 sql 文件来创建一个 Database 并在该 database 中添加 tables。
这是代码：

CREATE SCHEMA `employee_details`;
CREATE TABLE `employee_details`.`employee` (
    `emp_id` INT NOT NULL AUTO_INCREMENT,
    `name` VARCHAR(45),
    `dob` DATE,
    `joiningdate` DATE,
    `designation_id` INT,
    `gender` VARCHAR(45),
    `address` VARCHAR(90),
    `manager_id` INT,
    PRIMARY KEY (`emp_id`)
);

CREATE TABLE `employee_details`.`designation` (
    `designation_id` INT NOT NULL AUTO_INCREMENT,
    `designation` VARCHAR(45),
    `dept_id` INT,
    `salary` FLOAT,
    PRIMARY KEY (`designation_id`)
);

CREATE TABLE `employee_details`.`department` (
    `dept_id` integer NOT NULL AUTO_INCREMENT,
    `dept_name` VARCHAR(45),
    PRIMARY KEY (`dept_id`)
);

CREATE TABLE `employee_details`.`rating` (
    `emp_id` INT,
    `emp_rating` INT,
    `add_perks` FLOAT,
    `experience` INT
);

CREATE TABLE `employee_details`.`project_assign` (
    `emp_id` INT,
    `project_id` INT
);

CREATE TABLE `employee_details`.`project` (
    `project_id` INT NOT NULL AUTO_INCREMENT,
    `project_name` VARCHAR(45),
    `project_dept` INT,
    PRIMARY KEY (`project_id`)
);

ALTER TABLE employee 
ADD FOREIGN KEY (emp_id) REFERENCES rating(emp_id);

ALTER TABLE employee 
ADD FOREIGN KEY (emp_id) REFERENCES project_assign(emp_id);

ALTER TABLE employee 
ADD FOREIGN KEY (emp_id) REFERENCES employee(manager_id);

ALTER TABLE designation 
ADD FOREIGN KEY (designation_id) REFERENCES employee(designation_id);

ALTER TABLE designation 
ADD FOREIGN KEY (dept_id) REFERENCES department(dept_id);

ALTER TABLE department 
ADD FOREIGN KEY (dept_id) REFERENCES project(project_dept);

ALTER TABLE project 
ADD FOREIGN KEY (project_id) REFERENCES project_assign(project_id);

当我执行那个 sql 文件时，我得到以下错误：

15:16:50 ALTER TABLE employee ADD FOREIGN KEY (emp_id) REFERENCES rating(emp_id) 错误代码：1822。无法添加外键约束。引用表 'rating' 中的约束 'employee_ibfk_1' 缺少索引 0.000 秒

我在employee 和rating 中检查了emp_id 的数据类型。他们是一样的。我该如何解决这个错误？

Answer 1

你所有的外键关系都是倒退的。应该是：

ALTER TABLE rating
ADD FOREIGN KEY (emp_id) REFERENCES employee(emp_id);

所有其他外键都类似。