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