When to use NullBooleanField in Django : <p>I have a button that, when clicked, should save in the database that the user has drunk water. I just wanted to check whether NullBooleanField would be the correct way to define this.</p>

<p>A broader question that if answered would be useful to the community is a list of optimal circumstances under which to use NullBooleanField. But I'm not asking that here. Just in case you wanted a better challenge. </p>

<p>Thank you in advance.  </p>
