Littco has a good point. If you want to make the best use out of the database then you need to go through each and every question using the search function. I set up a word document and cut and paste any that I got wrong and then used that as a master list highlighting the areas I needed to bone up on.
As to the relevance of the database to the exams you are about to sit it will depend on whether you hit an exam where the CAA have introduced new questions that aren't yet picked up by BGS. I finished off a few months ago and as a rule of thumb I would say 70-80% of the exams were word for word from the database give or take a little bit of grammatical licence. The rest were variations of the same theme and only the occasional odd ball appeared that I hadn't seen. If you were to spend a month going through the database then you would clean up. Most people I have chatted to tended to only use the database in the final few weeks and very few actually bothered to go through every question.