Lists the most commonly used tags with empty/missing tag wikis (wiki or excerpt).
Q&A for ebook publishers and readers
SELECT Count, ('site://tags/' + TagName + '|' + TagName) AS TagName, ExcerptPostId AS [Post Link], WikiPostId AS [Post Link] FROM Tags t LEFT JOIN Posts pe ON pe.Id = t.ExcerptPostId LEFT JOIN Posts pw ON pw.Id = t.WikiPostId WHERE ExcerptPostId IS NULL -- no excerpt post OR WikiPostId IS NULL -- no wiki post OR LEN(pe.Body) = 0 -- excerpt empty OR LEN(pw.Body) = 0 -- wiki empty ORDER BY Count DESC