[英]Flask+SQLAlchemy thows OperationalError when trying to filter records by foreign key column
所以,我正在开发一个小博客风格的 web 应用程序作为个人项目。 我现在已经可以正常工作了,但是我在尝试对帖子进行评论时遇到了麻烦。
我设置帖子的方式是通过 SQLAlchemy ORM model model,它工作正常。 它具有内容和标题字段,以及与帖子作者的多对一关系,例如:
class Post(db.Model):
id = db.Column(db.Integer, primary_key = True)
title = db.Column(db.String(100), nullable=False)
date_posted = db.Column(db.DateTime, nullable=False, default=datetime.utcnow)
content = db.Column(db.Text, nullable=False)
feature_image = db.Column(db.String, nullable=True)
user_id = db.Column(db.Integer, db.ForeignKey('user.id'), nullable=False)
comments = db.relationship('Comment', backref='original_post', lazy=True)
我的评论遵循相同的结构,与帖子具有多对一的关系,如下所示:
class Comment(db.Model):
id = db.Column(db.Integer, primary_key = True)
date_posted = db.Column(db.DateTime, nullable=False, default=datetime.utcnow)
content = db.Column(db.Text, nullable=False)
post_id = db.Column(db.Integer, db.ForeignKey('post.id'), nullable=False)
user_id = db.Column(db.Integer, db.ForeignKey('user.id'), nullable=False)
因此,为了让评论显示在帖子下方,我试图从“post”表中查询“comment”表并过滤“post_id”,它应该与 post.id 匹配:
@app.route('/post/<int:post_id>')
def post(post_id):
post = Post.query.get_or_404(post_id)
comments = Comment.query.filter(Comment.original_post==post)
但是当我尝试加载帖子页面时,它会抛出以下错误:
sqlalchemy.exc.OperationalError: (sqlite3.OperationalError) no such column: comment.post_id
[SQL: SELECT comment.id AS comment_id, comment.date_posted AS comment_date_posted, comment.content AS comment_content, comment.post_id AS comment_post_id, comment.user_id AS comment_user_id
FROM comment
WHERE ? = comment.post_id]
[parameters: (1,)]
(Background on this error at: http://sqlalche.me/e/e3q8)
我查看了有关该主题的其他一些线程,这些线程在查询之前建议 a.join ,如下所示:
comments = Comment.query.join(Post).filter(Post.id == post_id).all()
但我得到一个类似的错误:
sqlalchemy.exc.OperationalError: (sqlite3.OperationalError) no such column: comment.post_id
[SQL: SELECT comment.id AS comment_id, comment.date_posted AS comment_date_posted, comment.content AS comment_content, comment.post_id AS comment_post_id, comment.user_id AS comment_user_id
FROM comment JOIN post ON post.id = comment.post_id
WHERE post.id = ?]
[parameters: (1,)]
我在 db 文件中的“评论”表只是缺少外键字段。
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