title: how to join table using alias without prefix in lumen
body: <p>it is my active sql:</p>
  
  <pre><code>SELECT sag.goods_id, if(sa.status=3, 1, 0) AS act_status 
  FROM d_seckill_activity_goods AS sag LEFT JOIN d_seckill_activity AS sa ON sa.id = sag.sa_id
  WHERE sa.id = 1
  </code></pre>
  
  <p>Then i need it using DB in lumen
  so i write like this:</p>
  
  <pre><code>$prefix = env('DB_PREFIX');
  DB::table('seckill_activity_goods as sag')
      -&gt;leftJoin('seckill_activity as sa', 'sa.id', '=', 'sag.sa_id')
      -&gt;select('sag.goods_id', DB::raw("if({$prefix}sa.status=3, 1, 0) AS act_status"))
      -&gt;first();
  </code></pre>
  
  <p>luckly it work well, but i hate the $prefix variable,</p>
  
  <p>is it another way using DB ?</p>