title: JOOQ - nested query
body: <p>I'm trying to write this query with jooq</p>
  
  <pre><code>SELECT region.*, 
         (SELECT COUNT(*)
          FROM city 
          WHERE city.region_id = region.id) AS num
  FROM region;
  </code></pre>
  
  <p>I tried few things, but no success. So far I got nothing more than</p>
  
  <pre><code>dsl.select().from(Tables.REGION).fetch();
  </code></pre>
  
  <p>How can I add the <code>num</code> column to my result? Any help appreciated.</p>