我有两个 SQLAlchemy 模型设置如下:
##############
# Post Model #
##############
class Post(db.Model):
id = db.Column(db.Integer, primary_key = True)
title = db.Column(db.String(250))
content = db.Column(db.String(5000))
timestamp = db.Column(db.Integer)
author_id = db.Column(db.Integer, db.ForeignKey('user.id'))
likes = db.relationship('Like', backref = 'post', lazy = 'dynamic')
###############
# Likes Model #
###############
class Like(db.Model):
id = db.Column(db.Integer, primary_key = True)
voter_id = db.Column(db.Integer, db.ForeignKey('user.id'))
post_id = db.Column(db.Integer, db.ForeignKey('post.id'))
如您所见,有一个帖子模型和一个用户喜欢这些帖子的模型。我想创建一个查询来选择所有帖子,按该帖子的喜欢数量排序。在 shell 中,我可以运行:
SELECT post.*,
count(like.id) AS num_likes
FROM post
LEFT JOIN like
ON post.id = like.post_id
GROUP BY post.id;
等效的 SQLAlchemy 命令是什么?
谢谢!
最佳答案
从原始查询到 Flask-SQLAlchemy 的转换非常机械:
db.session.query(Post, db.func.count(Like.id)).outerjoin(Like).group_by(Post.id)
关于python - SQLAlchemy 查询,加入关系并按计数排序,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/20290462/