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