What all do they do in a drug test?

I was just wandering what all they do in a drug test for work. I have to go to a medical center in pittsburgh for my drug test before I can start work for my new company and was just wondering what all they do. When I joined the military they did urine, blood, and mouth swab, do they do this for most civilian jobs to or is it just one? Im clean, just curious as to if I should hold my pee or not when I go lol.