title: Proc SQL and removing duplicates by a single variable
body: <p>PROC SQL newbie here - I want to use Proc SQL to concatenate (stack) ID and Race data from two different datasets, while also removing duplicates by ID only (and NOT by both ID and Race) - is this possible? For example, after combining the data below, I only want the first instance of ID=1 (where Race=white), and not both {(1, White) and (1, Black)}</p>
  
  <p>Sample Data:</p>
  
  <pre><code>DATA SAMPLE1;
      INPUT ID RACE$;
      DATALINES;
      1 WHITE
      2 BLACK
      3 WHITE
      4 BLANK
      ;
  RUN; 
  DATA SAMPLE2;
      INPUT ID RACE$;
      DATALINES;
      5 HISPANIC
      6 ASIAN
      7 HISPANIC
      8 ASIAN
      1 BLACK
      ;
  RUN;
  </code></pre>