title: Find_by returns first record
body: <p>When using <code>find_by</code> and just supplying an id param, <code>find_by</code> returns the first entry in the table.</p>
  
  <p>E.g.</p>
  
  <pre><code>@article = Article.find_by(params[:article_id])
  </code></pre>
  
  <p>returns article with <code>id = 1</code> while using <code>find</code> gives me the article with <code>id = :article_id</code></p>
  
  <p>Can somebody explain why find_by returns the record with the first id?</p>