title: SQL query with "not exists" not working
body: <p>I'm trying to use a simple query but I'm not getting anywhere.
  The objective is to "learn" how "not exists" works.
  I have a simple table with "idUsuario" as default ID for users and a name.</p>
  
  <pre><code>    SELECT * FROM usuario
      WHERE NOT EXISTS (
          SELECT * FROM usuario
          WHERE u.idUsuario =16
      )
  </code></pre>
  
  <p>Here i'm trying to get ALL the users from the table where the ID IS NOT 16. But it just get all of them.. What am I doing wrong?</p>
  
  <p>Thanks in advance!</p>