title: How can I select only one column using SQLAlchemy?
body: <p>I want to select (and return) one field only from my database with a "where clause". The code is:</p>
  
  <pre><code>from sqlalchemy.orm import load_only
      @application.route("/user", methods=['GET', 'POST'])
      def user():
          user_id = session.query(User, User.validation==request.cookies.get("validation")).options(load_only("id"))
          session.commit()
          return user_id
  </code></pre>
  
  <p>This fails and the traceback is:</p>
  
  <pre><code>File "/Library/Python/2.7/site-packages/flask/app.py", line 1836, in __call__
  return self.wsgi_app(environ, start_response)
  File "/Library/Python/2.7/site-packages/flask/app.py", line 1820, in wsgi_app
  response = self.make_response(self.handle_exception(e))
  File "/Library/Python/2.7/site-packages/flask/app.py", line 1403, in handle_exception
  reraise(exc_type, exc_value, tb)
  File "/Library/Python/2.7/site-packages/flask/app.py", line 1817, in wsgi_app
  response = self.full_dispatch_request()
  File "/Library/Python/2.7/site-packages/flask/app.py", line 1478, in full_dispatch_request
  response = self.make_response(rv)
  File "/Library/Python/2.7/site-packages/flask/app.py", line 1577, in make_response
  rv = self.response_class.force_type(rv, request.environ)
  File "/Library/Python/2.7/site-packages/werkzeug/wrappers.py", line 841, in force_type
  response = BaseResponse(*_run_wsgi_app(response, environ))
  File "/Library/Python/2.7/site-packages/werkzeug/wrappers.py", line 57, in _run_wsgi_app
  return _run_wsgi_app(*args)
  File "/Library/Python/2.7/site-packages/werkzeug/test.py", line 867, in run_wsgi_app
  app_rv = app(environ, start_response)
  TypeError: 'Query' object is not callable
  </code></pre>
  
  <p>How can I select and return just the "id" column? I have tried several other ways too but also with failure. Is "load_only" the correct option?</p>