Using iPhoto to delete items which weren't imported

As an iPhoto newbie, I ran into a problem.

I had a bunch of pictures in iPhoto, from my camera and used iPhoto to delete poor quality and redundant photos. But all that deleting them did was remove them from the library (because I didn't have iPhoto "import" my photos when adding them). So what did I do?

I moved all my pictures into the iPhoto library folder. Except for the ones which already had aliases in that folder (weren't deleted). I just dragged them and "applied to all" my decision to "not replace" duplicate items. Then I deleted everything in the iPhoto library, and moved the pictures I hadn't moved earlier into the library. Ta-da!