text: DROP DATABASE IF EXISTS employee_DB;
  
  CREATE DATABASE employee_DB;
  
  USE employee_DB;
  
  CREATE TABLE department(
      id INT PRIMARY KEY AUTO_INCREMENT,
      name VARCHAR(30) NOT NULL
  );
  
  CREATE TABLE role(
      id INT NOT NULL PRIMARY KEY AUTO_INCREMENT,
      title VARCHAR (30),
      salary DECIMAL NOT NULL,
      department_id INT NOT NULL,
      CONSTRAINT fk_department FOREIGN KEY (department_id) REFERENCES department(id)
  );
  
  CREATE TABLE employees(
      id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
      first_name VARCHAR(30) NOT NULL,
      last_name VARCHAR(30) NOT NULL,
      role_id INT NOT NULL,
      CONSTRAINT fk_role FOREIGN KEY (role_id) REFERENCES role(id),
      manager_id INT,
      CONSTRAINT fk_manager FOREIGN KEY (manager_id) REFERENCES employee(id)
  );
  
  SELECT
      *
  FROM
      department;
  
  SELECT
      *
  FROM
      role;
  
  SELECT
      *
  FROM
      employee;