title: how to do a join in sqlalchemy session query?
body: <p>I need to find the equivalent of this query in sqlalchemy.</p>
  
  <pre><code>SELECT u.user_id, u.user_name, c.country FROM
  table_user u , table_country c WHERE u.user_email = 'abc@def.com'
  </code></pre>
  
  <p>i tried this below code:</p>
  
  <pre><code>session.query(User).join(Country.country).filter(User.user_email == 'abc@def.com').first()
  </code></pre>
  
  <p>and this gave me below error :</p>
  
  <pre><code>  AttributeError: 'ColumnProperty' object has no attribute 'mapper'
  </code></pre>
  
  <p>can anyone give an example of join query with tables mapped to new class objects ?</p>