Subject Invoice Detail: Design / Normalization
Hello, I've posted this question in the "general" but the moderator told me it's a "support" question. So here I go again!

It's a design / normalization question: How to save Invoice detail correctly?

Each line on the invoice detail has its FK pointing to the Article's ID, but sometimes the user needs to modify or add some text to the article description just for that invoice. Or sometimes he/she needs to insert a "free" line (pointing to no article at all) just filling the description.

So my "big" doubt is: Is this a case for "denormalization" ? Should I add a "description" field to the invoice detail (and 90% of the time having exactly the same description of the article's table!!)

Or should I have the "description" field in a separate table. In this case I don't imagine how to update that table, as the user enters the data in a DBGrid (I work with Delphi / IBDac)

I hope I'm clear with my question!