擅长:python、mysql、java
<blockquote>
<p>You cannot use MyObject.query here, because SqlAlchemy tries to find a field to put result of avg function to, and it fails.</p>
</blockquote>
<p>这不是真的。<code>func.avg(Rating.field2).label('average')</code>返回一个<code>Column</code>对象(与给定的精确类型对象相同)。所以您可以将它与查询对象的<code>with_entities</code>方法一起使用。</p>
<p>以下是您的示例:</p>
<pre><code>Rating.query.with_entities(func.avg(Rating.field2).label('average')).filter(Rating.url == url_string.netloc)
</code></pre>