I work in R regularly and do most of my more complex data manipulation in R whenever I can, but most of these examples are simple enough that I think it makes s

I work in R regularly and do most of my more complex data manipulation in R whenever I can, but most of these examples are simple enough that I think it makes sense to keep them in SQL. The only ones that struck me as really weird to do in SQL were the cumulative cash flows and the "histograms"/binning one, though the ones requiring window functions might also be slightly easier in R than in SQL. Also, a lot of these would need to be done in SQL in practice since the data wouldn't fit in memory. Any solution that requires loading the table [login (user_id, timestamp)] into memory probably won't scale very well!