Firstly I tried it, from what i saw yes it has to be Unique or PK. Secondly I'm pretty sure I read somewhere where it has to be PK or unique. Thirdly I checked oradocs and some other pages, the closes thing I got to an answer
A foreign key constraint (also called a referential integrity constraint) designates a column as the foreign key and establishes a relationship between that foreign key and a specified primary or unique key, called the referenced key.
this implies, but doesn;t explicitly state that it HAS to be a PK or a UNIQUE.
Basically I want a simple yes/no answer just to give me some peace of mind. I don't mean to waste time, but oracle changes from time to time, and I'd rather get a confirmation from someone with more experience/knowledge.
Thanks!