text: DROP DATABASE IF EXISTS employees_db;
  
  CREATE DATABASE employees_db;
  
  USE employees_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 NOT NULL,
      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) NOT NULL,
      last_name VARCHAR(30) NOT NULL,
      role_id INT NOT NULL,
      manager_id INT NULL,
      PRIMARY KEY (id),
      FOREIGN KEY (role_id)
      REFERENCES role(id)
      ON DELETE CASCADE
  );