title: Will Eloquent automatically add this foreign key to the primary key's index?
body: <p>Let's say I have a parent and a child table, in Laravel, for table <code>Order</code>, my model would look like this:</p>
  
  <pre><code>public function up()
  {
      Schema::create('orders', function(Blueprint $table)
      {
          $table-&gt;integer('customer_id')-&gt;unsigned();
          $table-&gt;foreign('customer_id')-&gt;references('id')-&gt;on('customers')-&gt;onDelete('cascade');
  
          $table-&gt;increments('id');
  </code></pre>
  
  <p>I know Eloquent would consider <code>id</code> to be the primary key of <code>orders</code>, so an index would be automatically created on that primary key.</p>
  
  <p>What should I do to make sure that <code>customer_id</code> is part of the primary key's index, setup in that order:</p>
  
  <pre><code>1.  customer_id
  2.  id
  </code></pre>
  
  <p>Example of tables</p>
  
  <pre><code>      Customer
      +-------------+
      | id          | --&gt; primary key
      |- - - - - - -|
      | name        |
      | address     |
      +-------------+
             |
             |
             |
             A
        Order     
      +------------------+        
      | customer_id (fk) | --- primary key
      | id               | --- primary key        
      |- - - - - - - - - |
      | date             |
      +------------------+ 
  </code></pre>