title: Is there an "IF NOT EXISTS" clause for adding columns in MySql?
body: <p>I need to run this MySql code on some databases and I suspect that some of them to have already this column. Is there anything similar to <code>if not exists</code> for the below code?</p>
  
  <pre><code>ALTER TABLE 
      `comments` 
  ADD COLUMN 
      `active` int(1) NOT NULL DEFAULT '0' AFTER `sid`
  </code></pre>
  
  <p>I'm considering this to prevent getting the duplicated column error.</p>