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