How to detect how many observations in a dataset (or if it is empty), in SAS?

Question

I wonder if there is a way of detecting whether a data set is empty, i.e. it has no observations. Or in another saying, how to get the number of observations in a specific d

Answer 1

Proc sql is not efficient when we have large dataset. Though using ATTRN is good method but this can accomplish within base sas, here is the efficient solution that can give number of obs of even billions of rows just by reading one row:

data DS1;
set DS nobs=i;
if _N_ =2 then stop;
No_of_obs=i;
run;