Instead of the Left Outer Join, couldn't you also make it an Inner Join to S.BOOK_ID? The question, if I read it correctly, only requires you to return sales in Nov 2013. If there is no data for a book_id, you want to exclude it from your returned data, no?
I would imagine it is up to interpretation. It would probably be a good thing to ask the interviewer about to show that you are thinking about edge cases.
If it were me, I'd prefer to see those that made no sales based on the question. I guess if I didn't want to see them, I would ask for "where sales are greater than $0.00".
