docs: protected void appendGroupByClause(List groupByFields, StringBuffer buf)
      {
          if (groupByFields == null || groupByFields.size() == 0)
          {
              return;
          }
  
          buf.append(" GROUP BY ");
          for (int i = 0; i < groupByFields.size(); i++)
          {
              FieldHelper cf = (FieldHelper) groupByFields.get(i);
   
              if (i > 0)
              {
                  buf.append(",");
              }
  
              appendColName(cf.name, false, null, buf);
          }
      }