title: Rails: where vs map(&:attribute)
body: <p>Let's say we have 3 users <code>[User name="A"], [User name="B"], [User name="C"]</code></p>
  
  <p>Is there a difference between (to check presence):</p>
  
  <p><code>if User.where(name: "A").first</code></p>
  
  <p>and</p>
  
  <pre><code>User.all.map(&amp;:name).include? "A"
  </code></pre>
  
  <p>Thank you.</p>