text: DROP DATABASE IF EXISTS employee_db;
  CREATE DATABASE employee_db;
  
  USE employee_db;
  
  CREATE TABLE departments(
    id INT NOT NULL AUTO_INCREMENT,
    name VARCHAR(30),
    PRIMARY KEY (id)
  );
  
  CREATE TABLE roles(
    id INT NOT NULL AUTO_INCREMENT,
    title VARCHAR(30),
    salary DECIMAL(10, 2),
    department_id INT NOT NULL,
    FOREIGN KEY (department_id) REFERENCES departments(id),
    PRIMARY KEY (id)
  );
  
  CREATE TABLE employees(
    id INT NOT NULL AUTO_INCREMENT,
    first_name VARCHAR(30),
    last_name VARCHAR(30),
    role_id INT,
    FOREIGN KEY (role_id) REFERENCES roles(id),
    manager_id INT,
    FOREIGN KEY (manager_id) REFERENCES employees(id),
    PRIMARY KEY (id)
  );