title: Two different group by clauses in one query?
body: <p>First time posting here, a newbie to SQl, and I'm not exactly sure how to word this but I'll try my best.</p>
  
  <p>I have a query:</p>
  
  <pre><code>select report_month, employee_id, split_bonus,sum(salary) FROM empsal
  where report_month IN('2010-12-01','2010-11-01','2010-07-01','2010-04-01','2010-09-01','2010-10-01','2010-08-01') 
  AND employee_id IN('100','101','102','103','104','105','106','107')
  group by report_month, employee_id, split_bonus;
  </code></pre>
  
  <p>Now, to the result of this query, I want to add a new column <strong>split_bonus_cumulative</strong> that is essentially equivalent to adding a <strong>sum(split_bonus)</strong> in the select clause but for this case, the group buy should only have report_month and employee_id. </p>
  
  <p>Can anyone show me how to do this with a single query? Thanks in advance.</p>