Comment by codegeek

I would make a couple of assumptions:

- price could be 0.0 for a book

- Total sales means the sum and not count

- Date format will be yyyymmdd (if not, assume that we converted in Oracle or Sybase)

    SELECT a.name, SUM(s.price) FROM authors a
    INNER JOIN books b ON (a.id=b.author_id)
    LEFT OUTER JOIN sales s ON (b.id = s.book_id)
    GROUP BY a.name
    HAVING (s.date >= '20131101' AND s.date <= '20131130')