[Zombies][1] are questions with no upvoted answers.
I came up with this [SEDE query][2] to find answers with zero votes on questions that have no accepted answer and no answers with greater than zero score.
In other words, answers on questions that show up on the *Unanswered* tab,
until the answer receives an upvote. (Latest version is [here][3], FYI, not subject for review.)

    DECLARE @username AS NVARCHAR(60) = ##DisplayName:string? ##;
    DECLARE @userId AS INT = ##UserId:int?-1##;
    
    SELECT TOP 100
      u.Id AS [User Link],
      a.Id AS [Post Link],
      a.CreationDate
    FROM Posts a
      JOIN Users u ON a.OwnerUserId = u.Id
      JOIN (
        SELECT q.Id, MAX(a.Score) MaxAnswerScore
        FROM Posts q
        JOIN Posts a ON a.ParentId = q.Id
        WHERE q.AcceptedAnswerId IS NULL
        GROUP BY q.Id
      ) q
      ON a.ParentId = q.Id
    WHERE 
      (@username = '' OR u.DisplayName = @username)
      AND (@userId = -1 OR u.Id = @userId)
      AND a.Score = 0
      AND q.MaxAnswerScore = 0
    ORDER BY a.CreationDate DESC

Is there a better way to write this?
Can it be improved?


  [1]: https://codereview.meta.stackexchange.com/a/1511/12390
  [2]: http://data.stackexchange.com/codereview/revision/265223/346617/forgotten-zombie-killers
  [3]: http://data.stackexchange.com/codereview/query/265223/forgotten-zombie-killers