title: laravel OrderBy and sum
body: <p>This question seems so silly but it's annoying me.</p>
  
  <pre><code> ----------------------------------------------------------------
   | account_id | order_id | sales | profit | currency | date     |
   |---------------------------------------------------|-----------
   |    10      |   100    | 550   |  10    | USD      |2016-10-11|
   |    10      |   101    | 144   |  4     | NZD      |2016-10-12|
   |    9       |   102    | 429   |  44    | NZD      |2016-10-13|
   |    10      |   103    | 797   |  80    | NZD      |2016-10-14|
   ----------------------------------------------------------------
  </code></pre>
  
  <p>I want to sum of profit by currency</p>
  
  <pre><code>$account = App\Account::find(10);
  
  $collection = $account
                  -&gt;orders()                # relation between order and account
                  -&gt;completedLastMonth()    # scope of dates,
                  -&gt;groupBy('currency')     # group by currency
                  -&gt;sum('profit')           # sum of profit
  </code></pre>
  
  <p>but the <code>$collection</code> is 94.</p>
  
  <p>So I want result something like this</p>
  
  <pre><code>$collection = [
      'USD' =&gt; 10,       # total profit of USD 10 for account 10
      'NZD' =&gt; 84        # total profit of NZD 80 + 4 = 84 for account 10
  ]
  </code></pre>
  
  <p><strong>I have logic of relation between account and Orders and Last Month Scope, Please help me for Aggregate SUM and GROUP BY</strong></p>