title: Cursor inside SQL query
body: <p>In Oracle, it's possible to return a <code>cursor</code> inside a SQL query, using the <code>cursor</code> keyword, like this:</p>
  
  <pre><code>select owner, table_name,
      cursor (select column_name 
          from all_tab_columns
          where owner = allt.owner 
          and table_name = allt.table_name) as columns
  from all_tables allt
  </code></pre>
  
  <p>The questions are:</p>
  
  <ol>
  <li>Does anyone know where can I find documentation for this?</li>
  <li>Does PortgreSQL (or any other open source DBMS) have a similar feature?</li>
  </ol>