Using The DISTINCT Keyword

Hi all,

I have two datatables in my database. The first table, named Books, has two columns: BookID and Author (BookID is the primary key). The second table, named Purchases, has three columns: PurchaseID, BookID, BuyerID (Purchase ID is the primary key).

The idea here is that the Books datatable contains information regarding the book and its author while the Purchases datatable contains information on who has purchased what book.

Now, say I want to write an SQL query to extract a list of all the authors who have written a book purchased by buyer X. How would I go about doing this without having any duplicate entries? I figured that the following would work:

SELECT DISTINCT * FROM Books INNER JOIN Purchases ON Books.BookID=Purchases.BookID

But this ends up generating duplicate BookIDs if the Purchases table contains several buyers who have bought that Book. I know I could use BookID rather than * in the above query and that would work, but in reality I'm dealing with more complex tables and I would rather keep the * in there to actually get all the data out in one go.