text: -- Create database
  DROP DATABASE IF EXISTS employees_db;
  CREATE DATABASE employees_db;
  USE employees_db;
  
  -- Create department table
  CREATE TABLE department (
    id INT NOT NULL AUTO_INCREMENT,
    name VARCHAR(30) NULL,
    PRIMARY KEY (id)
  );
  
  -- Create role table
  CREATE TABLE role (
    id INT NOT NULL AUTO_INCREMENT,
    title VARCHAR(30) NOT NULL,
    salary DECIMAL(10,2) NOT NULL,
    department_id INT, 
    CONSTRAINT fk_department FOREIGN KEY (department_id) REFERENCES department(id)  ON DELETE SET NULL,
    PRIMARY KEY (id)
  );
  
  -- Create Employee table
  CREATE TABLE employee (
    id INT NOT NULL AUTO_INCREMENT,
    first_name VARCHAR (30) NOT NULL,
    last_name VARCHAR(30) NOT NULL,
    role_id INT, 
    CONSTRAINT fk_role FOREIGN KEY (role_id) REFERENCES role(id) ON DELETE SET NULL,
    manager_id INT, 
    CONSTRAINT fk_manager FOREIGN KEY (manager_id) REFERENCES employee(id) ON DELETE SET NULL,
    PRIMARY KEY (id)
  );