text: DROP TABLE IF EXISTS employee;
  DROP TABLE IF EXISTS roles;
  DROP TABLE IF EXISTS department;
  
  CREATE TABLE department (
      department_id INTEGER AUTO_INCREMENT PRIMARY KEY,
      department_name VARCHAR(50) NOT NULL
  );
  
  CREATE TABLE roles (
      role_id INTEGER AUTO_INCREMENT PRIMARY KEY,
      role_name VARCHAR(50) NOT NULL,
      department_id INTEGER,
      salary DECIMAL(10,2) NOT NULL,
      CONSTRAINT fk_department FOREIGN KEY (department_id) REFERENCES department(department_id) ON DELETE CASCADE
  );
  
  CREATE TABLE employee (
      employee_id INTEGER AUTO_INCREMENT PRIMARY KEY,
      first_name VARCHAR(50) NOT NULL,
      last_name VARCHAR(50) NOT NULL,
      role_id INTEGER,  
      manager_id INTEGER,
      FOREIGN KEY (role_id) REFERENCES roles(role_id) ON DELETE CASCADE  
  );
  
  