title: Eloquent model add extra column by default
body: <p>I have a model called <code>Book</code> and I want to add an extra column to the default SQL.</p>
  
  <p>At the moment the default sql looks like this:</p>
  
  <pre><code>SELECT * FROM `books`
  </code></pre>
  
  <p>But I want the default SQL to look like this:</p>
  
  <pre><code>SELECT *, "Hello" as `greeting` FROM `books`
  </code></pre>
  
  <p>So that I can do the following:</p>
  
  <pre><code>// in a controller function...
  $book = Book::find(1);
  echo $book-&gt;greeting; // Hello
  
  $books = Book::all();
  foreach($books as $book){
      echo $book-&gt;greeting; // Hello
  }
  </code></pre>
  
  <p>Is there any way I can achieve this?</p>
  
  <p>Many thanks</p>