A beginner can handle squatting AND deadlifting in every single session. Remember, for a starting weight for deadlift we're only talking 135lbs. Unless you are under 100lbs or infirm that's not going to really smash you the way it will later at 225 or 315lbs.
As I wrote above, I frequently have my clients squat and deadlift in the same session, and twice a week. They do alright, and increase the weights each session or week. Again, once they hit SQ100% and DL125% or so, it'll be harder for them to SQ+DL in each session, and anyway they'll be well-practiced at the movements and ready for more.
However, if you for some reason will or can do only squat or deadlift in a session, I would have more squatting than deadlifting - only because SQ has a lot of carryover to DL, but DL much less carryover to SQ. Their DL will get stronger with lots of squatting, but their squat won't get much stronger with lots of deadlifting.