title: How to detect how many observations in a dataset (or if it is empty), in SAS?
body: <p>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 data set.</p>
  
  <p>So that I can write an If statement to set some conditions.</p>
  
  <p>Thanks.</p>