Something which I am starting to believe is that there is sometimes a clear divide between candidates that enjoy programming as a hobby versus those who consider it "just a day job".
Even if you don't know the answer to a specific question it is worth mentioning that normally you'd look up the answer on < your favourite resource > (eg. StackOverflow).
Based on your experience I don't think the interviewer will expect that you'll get every question right. They're most likely trying to decide if you've got "potential".
So relax and try to enjoy it!
