text: DROP DATABASE IF EXISTS employees;
  CREATE DATABASE employees;
  USE employees;
  CREATE TABLE department (
      id INT unsigned AUTO_INCREMENT primary key,
      name VARCHAR(30) UNIQUE NOT NULL
  );
  CREATE TABLE role (
      id INT unsigned AUTO_INCREMENT primary key,
      title VARCHAR(30) UNIQUE NOT NULL,
      salary DECIMAL unsigned NOT NULL,
      department_id INT unsigned NOT NULL
  );
  CREATE TABLE employee (
      id INT unsigned AUTO_INCREMENT primary key,
      first_name VARCHAR(30) UNIQUE NOT NULL,
      last_name VARCHAR(30) UNIQUE NOT NULL,
      role_id INT unsigned NOT NULL,
      manager_id INT unsigned NOT NULL
  );