text: DROP DATABASE IF EXISTS employees_db;
  CREATE DATABASE employees_db;
  USE employees_db;
  
  
  CREATE TABLE departments(
  	id INTEGER AUTO_INCREMENT, 
      name VARCHAR(255) NOT NULL,
      PRIMARY KEY(id)
  );
  
  CREATE TABLE roles(
  	id INTEGER AUTO_INCREMENT,
  	title VARCHAR(255) NOT NULL,
      PRIMARY KEY(id)
  );
  
  CREATE TABLE managers(
  	id INTEGER AUTO_INCREMENT,
  	name VARCHAR(255) NOT NULL,
      PRIMARY KEY(id)
      );
  
  CREATE TABLE employees(
      id INTEGER AUTO_INCREMENT,
      first_name VARCHAR(255) NOT NULL,
      last_name VARCHAR(255),
      salary INTEGER NOT NULL,
      role_id INTEGER NOT NULL,
      CONSTRAINT fk_role_id FOREIGN KEY (role_id) REFERENCES roles(id) ON DELETE CASCADE,
      department_id INTEGER NOT NULL,
  	CONSTRAINT fk_department_id FOREIGN KEY (department_id) REFERENCES departments(id) ON DELETE CASCADE,
      manager_id INTEGER NOT NULL,
      CONSTRAINT fk_manager_id FOREIGN KEY (manager_id) REFERENCES managers(id) ON DELETE CASCADE,
      PRIMARY KEY(id)
  );
  -- Call for all needed table data
  /*
  SELECT
  employees.id as ID, 
  employees.first_name as first_name, 
  employees.last_name as last_name,
  roles.title as title,
  departments.name as department,
  managers.name as manager,
  salary
  FROM
  employees
  LEFT JOIN
  departments
  ON (employees.department_id = departments.id)
  LEFT JOIN
  roles
  ON (employees.role_id = roles.id)
  LEFT JOIN
  managers
  ON (employees.manager_id = managers.id)
  */