Question

我想按照收到的帖子的数量来查询查询结果。这是我的表：

class Card(Base):
   __tablename__ = 'cards'
   id = Column(Integer, primary_key=True)
   post_id = Column(Integer)
   voted = Column(Boolean)

@hybrid_property
def likes(self):
   likes = session.query(Card).filter(and_(Card.post_id == self.post_id, Card.voted == True)).count()
   return likes

@likes.expression
def likes(cls):
   return (select([func.count(Card.id)]).where(and_(Card.post_id == cls.post_id, Card.voted == True))

这是查询：

cards = session.query(Card).filter(Card.user_id == current_user.get_id()).order_by(desc(Card.likes)).all()

SQL中的order_by部分，对我来说似乎很合适：

ORDER BY (SELECT count(cards.id) AS count_1 FROM cards WHERE cards.post_id = cards.post_id AND cards.voted = true) DESC

但是当我在查询后调用它时：

for card in cards:
    print card.likes

输出不是降序，而是完全随机的顺序。我现在唯一的猜测是，由于过滤器，计数只在card.user_id == current_user.id的卡上执行。如果是这样（？），我如何按照帖子收到的总数来订购我的查询结果？

之前我查过的内容：混合属性1，SQLAlchemy按混合属性排序2，

谢谢。

Answer 1

老实说，我看不出你的sql语句是如何工作的，下面是对postgresql命令的引用。

http://www.postgresql.org/docs/9.4/static/queries-order.html http://www.tutorialspoint.com/postgresql/postgresql_having_clause.htm

我相信你的查询应该像这样重写：

SQL：

SELECT count(cards.id) AS count_1, cards.id
FROM cards
GROUP BY count_1
HAVING cards.voted = true
ORDER BY count_1 DESC

但即使这样，我看起来也不对，我们能看到你的ERD吗？

SQLAlchemy：按计数排序查询

1 个答案:

SQL：