title: Copy unique data from one table to another
body: <p>I have two tables. <code>Table A</code> is the main table, and <code>table B</code> an auxiliary table. Now i need to copy from <code>table B</code> to <code>table A</code> only the rows with a <code>aux_id</code> not present in <code>table A</code></p>
  
  <p><strong>table_A</strong></p>
  
  <pre><code>id |aux_id | firstname | lastname
  </code></pre>
  
  <p><strong>table_B</strong></p>
  
  <pre><code> aux_id | firstname | lastname
  </code></pre>
  
  <p>What I am trying, but apparently without success.</p>
  
  <pre><code>INSERT INTO table_A(aux_id,firstname,lastname)(SELECT aux_id,firstname,lastname FROM table_B WHERE aux_id != aux_id);
  </code></pre>
  
  <p>I am getting : <code>INSERT 0 0</code></p>
  
  <p>This is wrong, because i am sure that I have new entries in table B.</p>