title: Updating all created_at rows to be 10 minutes before in Ruby Sequel
body: <p>I am trying to take all the <code>created_at</code> timestamps in my table and decrement around 10 minutes from it (600 seconds). But I can't seem to figure it out.</p>
  
  <pre><code>MyApp::Model::MyTable.select(:created_at).update(:created_at =&gt; :created_at - 600)
  </code></pre>
  
  <p>I select all the rows from the <code>created_at</code> column and perform an update on said row so that each row is now <code>created_at</code> - 600 seconds (10 minutes). However, when I try this, it says <code>incompatible data types in combination</code>. </p>
  
  <p>Can someone give me a better solution to this?</p>