title: SQLAlchemy: create an intentionally empty query?
body: <p>What's the best way to create an intentionally empty query in SQLAlchemy?</p>
  
  <p>For example, I've got a few functions which build up the query (adding <code>WHERE</code> clauses, for example), and at some points I know that the the result will be empty.</p>
  
  <p>What's the best way to create a query that won't return any rows? Something like Django's <code>QuerySet.none()</code>.</p>