title: What does it mean for Rails merge to win a where clause?
body: <p>The rails <a href="http://guides.rubyonrails.org/active_record_querying.html#joins" rel="nofollow noreferrer">guide</a> says, "If we do want the last where clause to win then Relation#merge can be used."</p>
  
  <p>In the below example, why use merge if you can just have <code>User.where(User.inactive)</code>?</p>
  
  <pre><code>User.active.merge(User.inactive)
  # SELECT "users".* FROM "users" WHERE "users"."state" = 'inactive'
  </code></pre>