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