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