text: DROP DATABASE IF EXISTS employees_db;
  CREATE DATABASE employees_db;
  
  USE employees_db;
  
  CREATE TABLE departments (
      id INTEGER NOT NULL AUTO_INCREMENT,
      dept_name VARCHAR(30),
      PRIMARY KEY(id)
  );
  
  CREATE TABLE employees (
      id INTEGER NOT NULL AUTO_INCREMENT,
      first_name VARCHAR(30),
      last_name VARCHAR(30),
      role_id INTEGER,
      manager_id INTEGER 
      REFERENCES employee(id),
      FOREIGN KEY (role_id)
      REFERENCES roles(id)
      ON DELETE SET NULL,
      PRIMARY KEY(id)
  );
  
  CREATE TABLE roles (
      id INTEGER NOT NULL AUTO_INCREMENT,
      title VARCHAR(30),
      salary DECIMAL,
      department_id INTEGER,
      FOREIGN KEY (department_id)
      REFERENCES departments(id)
      ON DELETE SET NULL,
      PRIMARY KEY(id)
  );
  