I'm interested in business analyst type jobs that still involve some type of technical / development activities working with data. I've gone through the free SQL problems but there's only like 15 of them and like 70 problems overall. Would it still be worth it to pay for the other problems?
nope...
What should I focus on? Would it be better to focus on general database theory concepts?
BAs are more like business people with some technical literacy. I assume KPMG should already gave you enough privilege to enter this area, unless you really want to do technical stuffs which do require some formal training.