title: SQL select rows that dont have a join pair
body: <p>How can i do something like an opposite of join? For example from those two tables select values from table <strong>alice</strong> that are not in table <strong>bob</strong>:</p>
  
  <pre><code>alice:
  id|name
  --+----
  1 |one
  2 |two
  3 |three
  6 |six
  7 |seven
  
  bob:
  id|a_id
  --+----
  15|1
  16|2
  17|3
  </code></pre>
  
  <p>to get this:</p>
  
  <pre><code>result:
  name
  ----
  six 
  seven
  </code></pre>