title: MYSQL auto set expiry date
body: <p>i'm in new project and i need to set an expiry date to every post,
  so that i could make an mysql event do delete all the posts that reached the expiry date.
  i tried this:</p>
  
  <pre><code>alter table anuncios
  MODIFY dataexpiracao TIMESTAMP on update TIMESTAMPADD(DAY,30,'NOW()');
  </code></pre>
  
  <p>that gives me an error f syntax... pls help me
  i don't know if it is the best sollution but that's the unique i could found out after some research, if you know some other pls tell me and can you tell how to make the mysql event too?</p>