title: MySQL default value using another column
body: <p>I have a table</p>
  
  <pre><code>-------------
  | id | date |
  -------------
  </code></pre>
  
  <p>Now i need to add column "week", so is it possible to add column like</p>
  
  <pre><code>alter table `a` add column `week` INT(6) not null default DATE_FORMAT(`date`, '%Y%v')
  </code></pre>
  
  <p>?</p>