One of the simplest bits of advice I could give to anyone going for an interview.

If you don't know the answer to a question, tell the interviewer. There is little point in trying to answer somethnig with a load of ramblings if you don't know the answer. I only started my job a few months back but there were silly questions which I could not answer during the interview - ones which I knew but stuttered on.

The key was that I didn't make myself look foolish with a silly answer and that the rest of my technical knowledge came through during the interview process.

The interviewer will respect the fact that interviews can be a nervy place to be and also they know you don't know every single detail about SQL Server.

Just because you don't answer 1 or 2 questions doesn't mean you won't get the job. Demonstrating a sound alround knowledge and a willingness to improve in every area of the job (including the ones you know very well) will get you looked upon favourably.