此结构中的表
departmentspositionsemployeessalariesleave_requests
表结构（SQL）
MySQL 方言的 DDL。在编辑器中打开可获得可编辑的可视化 ER 图，或直接将 SQL 复制到你的项目中。
CREATE TABLE departments (
id INT PRIMARY KEY AUTO_INCREMENT,
name VARCHAR(100) NOT NULL UNIQUE,
cost_center VARCHAR(20)
);
CREATE TABLE positions (
id INT PRIMARY KEY AUTO_INCREMENT,
title VARCHAR(100) NOT NULL,
level VARCHAR(20) NOT NULL
);
CREATE TABLE employees (
id INT PRIMARY KEY AUTO_INCREMENT,
department_id INT NOT NULL,
position_id INT NOT NULL,
manager_id INT,
full_name VARCHAR(120) NOT NULL,
email VARCHAR(254) NOT NULL UNIQUE,
hired_at DATE NOT NULL,
FOREIGN KEY (department_id) REFERENCES departments(id),
FOREIGN KEY (position_id) REFERENCES positions(id),
FOREIGN KEY (manager_id) REFERENCES employees(id)
);
CREATE TABLE salaries (
id INT PRIMARY KEY AUTO_INCREMENT,
employee_id INT NOT NULL,
amount DECIMAL(12,2) NOT NULL,
currency VARCHAR(3) NOT NULL,
effective_from DATE NOT NULL,
FOREIGN KEY (employee_id) REFERENCES employees(id)
);
CREATE TABLE leave_requests (
id INT PRIMARY KEY AUTO_INCREMENT,
employee_id INT NOT NULL,
start_date DATE NOT NULL,
end_date DATE NOT NULL,
type VARCHAR(30) NOT NULL,
status VARCHAR(20) NOT NULL,
FOREIGN KEY (employee_id) REFERENCES employees(id)
);