The "Unanswered" button gives a page with already answered questions, just those not already concluded/checked as answered as well as those that don't have an answer with an upvote.
Where can I find a list of all the questions that have no answers (zero answers, or 0 answers)?
No, there isn't. Unanswered used to be exactly that, but this way it was found that just one answer, even if not helpful at all, excluded the question from the list. It was much less likely to get answered again.
Maybe a threshhold would be interesting: show me unanswered questions with at most n answers.
Edit This was true at the time of writing.
Now to find zero (0) answers, include the following in the search query:
This will result in all questions with no answer. If you use another number, it shows all questions with a minimum of so many answers. (answers:1 returns all questions with at least one answer.)
I believe what the unanswered button displays is all questions that have no accepted answer and no answer with at least one upvote. I believe the theory behind this is, if the question doesn't have an upvoted answer, there must not be a "good" answer yet. Additionally, I think this works well because it can add traffic to the question and get people to upvote a good answer that hasn't been seen yet.
The current unanswered view works the way it does because users asked for it to behave that way.
That is, it originally showed exactly what you're asking for now, but in practice it turned out that this is much less useful than showing questions with no upvoted or accepted answers for reasons mentioned by others. So someone filed a uservoice request, and enough people voted for it that it got the team's attention and was implemented.
That said, the current unanswered view is broken because you can't get a meaningful sort order. The "newest" questions just match the front page early, and never change if you go to the last page. Questions in the "votes" sort have the same problem: the highest voted won't change, and the lowest voted match the front page. The "my tags" sort is just a more targeted version of "newest". When you're viewing unanswered questions, what you're really looking for is a way to find old questions that you haven't seen before that perhaps you could answer.
https://blog.stackoverflow.com/2010/11/the-horror-of-no-answer-revival-and-necromancer/
This is now possible.
Not in the platform. The unanswered page, as mentioned, shows both unanswered questions and questions with no upvoted answers.
You can find unanswered questions using the data dump however. Brent Ozar has a post about just this.
Would be a good idea. Scope to pick up questions that the masses have skipped.
It is possible now using the built-in search. See my answer here.
