Could drinking the night before taking a blood pressure test effect the results?

Yes: Large amounts of alcohol can cause constriction of the arteries, leading to significant elevation in blood pressure.

Yes: Depending on when you go to get your blood pressure checked and what your diet was, you could have more fluid on your body. You could also get dehydrated as well which could have an opposite effect. Long term drinking can also raise your blood pressure independently if it's done in excess. The quantity of alcohol also matters.

Blood pressure.: Yes. If you were out drinking the night before, the withdrawal from alcohol can raise your blood pressure and heart rate.