text: DROP DATABASE IF EXISTS employee_DB;
  CREATE DATABASE employee_DB;
  
  USE employee_DB;
  
  
  CREATE TABLE department(
      id INTEGER(10) AUTO_INCREMENT NOT NULL,
      name VARCHAR(30) NOT NULL,
      PRIMARY KEY (id)
  );
  
  CREATE TABLE role(
      id INTEGER(10) AUTO_INCREMENT NOT NULL,
      title VARCHAR(30) NOT NULL,
      salary DECIMAL,
      department_id INT,
      PRIMARY KEY (id)
  );
  
  CREATE TABLE employee(
      id INTEGER(10) 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 (id),
      FOREIGN KEY (role_id) REFERENCES role(id),
      FOREIGN KEY (manager_id) REFERENCES role(id)
  );
  
  
  SELECT * FROM department;
  SELECT * FROM role;
  SELECT * FROM employee;