title: meaning of group by 1,2,3,4
body: <p>Someone can explain the code below to me? I am confused by Group by 1, 2, 3, 4, because there is no variable and value called 1, 2, 3, 4. </p>
  
  <pre><code>proc sql; create table SampleData as select
  uniqID, Category, Grade, Value,
  
  count(uniqID) as CNT,
  avg(PRICE) as APR,
  avg(Value) as ALE
  
  from DataIn where date ge &amp;intdt. group by 1,2,3,4;
  quit;
  </code></pre>