I have two datasets with the same variables on them that I'd like to append. The only problem is that they both have an ID variable that starts at 1 and increments for each record. When I append them, I want to take the last value of ID in the first dataset and add it to the values of ID in the second dataset, so that when they're appended I have a unique ID variable for each entry that increases as you go down the set.
The main issue is that both of these datasets are big - as in "takes 5 minutes to just run a basic data step on them" big. So while I can think of a few ways to do what I want, they all involve processing one or other of the datasets multiple times, resulting in a slow process. Is there a quick way to do it?
(Small edit to add info: generally, the second dataset is smaller than the first, so it's a little quicker to access as well if that affects the solution.)