title: Updating current value in ActiveRecord (Rails)
body: <p>in my application lots of objects are already preloaded by Rails.</p>
  
  <p>Now I like to update some of these object attributes. Unfortunately some of these objects are related to the same object in my database. When I add a value to myObject.balance (<code>myObject.balance += value</code>), the attribute balance in <em>differentButSameObject</em> has still the same value.</p>
  
  <p>One solution could be reloading the object. I would prefer to update the value like this:
  <code>UPDATE myTable SET balance = balance + 10 WHERE id = 1</code>.</p>
  
  <p>Is this possible?</p>