title: counting of unique entries of 2 columns
body: <p>I have the following table:</p>
  
  <pre><code>Schema::create('tracks', function (Blueprint $table) {
          $table-&gt;bigIncrements('id');
          $table-&gt;integer('user_id')-&gt;unsigned()-&gt;nullable()-&gt;index();
          $table-&gt;foreign('user_id')-&gt;references('id')-&gt;on('users')-&gt;onDelete('cascade');
          $table-&gt;string('ip');
          $table-&gt;string('session');
          $table-&gt;string('roboname')-&gt;nullable();
          $table-&gt;string('language');
          $table-&gt;string('referer');
          $table-&gt;string('path');
          $table-&gt;string('device');
          $table-&gt;string('screensize');
          $table-&gt;string('browser');
          $table-&gt;string('browser_version');
          $table-&gt;string('os');
          $table-&gt;string('os_version');
          $table-&gt;string('url');
          $table-&gt;string('full_url');
          $table-&gt;boolean('is_mobile');
          $table-&gt;boolean('is_tablet');
          $table-&gt;timestamps();
      });
  </code></pre>
  
  <p>i want to count all unique entries of session and path. What is the best way to do this?
  example:</p>
  
  <pre><code>session | path
  123 /test
  123 /test1
  123 /test
  321 /test
  321 /test
  </code></pre>
  
  <p>The result here would be 3.</p>