How do I transfer user data on delete

UPDATE employees
LEFT OUTER JOIN user
    ON "{your condition}"
SET  employee.foreign_key = user.foreign_key
WHERE {condition}

class User < ActiveRecord::Base
  before_destroy :assign_courses

  private

  def assign_courses
    new_user = User.new_user_responible #some way of finding the next user responsible
    courses.update_all(user: new_user)
  end
end

assign_questions