text: DROP DATABASE IF EXISTS ems_db;
  CREATE DATABASE ems_db;
  
  USE ems_db;
  
  CREATE TABLE department (
    department_id INT AUTO_INCREMENT NOT NULL,
    department_name VARCHAR(30) NULL,
    PRIMARY KEY (department_id)
  );
  
  CREATE TABLE roles (
    role_id INT AUTO_INCREMENT NOT NULL,
    employee_title VARCHAR(30) NOT NULL,
    employee_salary DECIMAL NOT NULL,
    department_id INT NOT NULL,
    PRIMARY KEY (role_id),
    FOREIGN KEY (department_id) REFERENCES department(department_id)
  );
  
  CREATE TABLE employee (
    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,
    PRIMARY KEY (employee_id),
    FOREIGN KEY (role_id) REFERENCES roles(role_id),
    FOREIGN KEY (manager_id) REFERENCES employee(employee_id)
  );
  
  