title: How to create a mysql column (seconds) calculated from an other column (timestamp)?
body: <p>I need to create a column of seconds calculated from an already existing column of timestamp called 'time'. I tried with a query with  unix_timestamp but it doesn't accept a thing like:</p>
  
  <pre><code>UPDATE tempLog SET seconds= UNIX_TIMESTAMP('time')
  </code></pre>
  
  <p>I'm a beginner in stackoverflow and mysql, thanks.</p>