These were my reasons exactly. I was originally writing a method that would check for pre-existing key and then present options, etc. but was hoping to keep the process as simple as possible for the end user... You know, if they enter the same ISBN twice, it just uses the latest entered data... Transparent to the user. I came across the DUPLICATE KEY thing while browsing and thought maybe I could shoehorn it into my needs... That's why I asked for how people were using it before I showed my own or my reasons... I suppose it makes a little more sense now.

I guess I can still make it transparent to the user, it'll just require more code for the system... Not really a big deal.

I appreciate your input though,
cidaris