title: GROUP BY clause order omitting results in Oracle 11g query
body: <p>I have a simple query that appears to give the desired result:   </p>
  
  <pre><code>select op.opr, op.last, op.dept, count(*) as counter 
  from DWRVWR.BCA_M_OPRIDS1 op
  where op.opr = '21B'
  group by op.opr, op.last ,op.dept;
  </code></pre>
  
  <p>My original query returns no results.  The only difference was the order of the group by clause:   </p>
  
  <pre><code>select op.opr, op.last, op.dept, count(*) as counter 
  from DWRVWR.BCA_M_OPRIDS1 op
  where op.opr = '21B'
  group by op.opr, op.dept, op.last;
  </code></pre>
  
  <p>In actuality, this was part of a much larger, more complicated query, but I narrowed down the problem to this.  All documentation I was able to find states that the order of the group by clause doesn't matter.  I really want to understand why I am getting different results, as I would have to review all of my queries that use the group by clause, if there is a potential issue.  I'm using SQL Developer, if it matters.   </p>
  
  <p>Also, if the order of the group by clause did not matter and every field not used in an aggregate function is required to be listed in the group by clause, wouldn't the group by clause simply be redundant and seemingly unnecessary?   </p>