Sql 炼金术 sqlalchemy.exc.NoReferencedTableError 没有创建表格

Question

我正在使用 flask 并尝试学习 sqlalchemy，我有一个数据库，我在其中添加了第三个 table 来制作新功能，但整个项目停止工作，它说：

sqlalchemy.exc.NoReferencedTableError: Foreign key associated with column 'url_reference.folder_rel' could not find table 'reffolders' with which to generate a foreign key to target column 'id'

这是dbs.py

from . import db
from flask_login import UserMixin
from sqlalchemy.sql import func
  
class User(db.Model, UserMixin):
    id = db.Column(db.Integer, primary_key=True)
    email = db.Column(db.String(200), unique=True)
    user_password = db.Column(db.String(150))
    user_name = db.Column(db.String(400))
    user_refs = db.relationship("RefFolders")

class RefFolders(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    folder_title = db.Column(db.String(1000))
    date_added = db.Column(db.DateTime(timezone=True), default=func.now())
    user_rel = db.Column(db.Integer, db.ForeignKey("user.id"))
    url_rel = db.relationship("UrlReference")

class UrlReference(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    ref_title = db.Column(db.String(1000))
    ref_url = db.Column(db.String(30000))
    date_added = db.Column(db.DateTime(timezone=True), default=func.now())
    folder_rel = db.Column(db.Integer, db.ForeignKey("reffolders.id"))

这是我在 __init__.py:

中创建数据库的地方

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from os import path
from flask_login import LoginManager

db = SQLAlchemy()
 
DB_NAME = "database.db"
 
def app():
    app = Flask(__name__)
    app.config['SECRET_KEY'] = '<here is the key in my code>'
    app.config['SQLALCHEMY_DATABASE_URI'] = f"sqlite:///{DB_NAME}"
    db.init_app(app)
 
    # making the blueprints usable
  
    from .views import views
    from .auth import auth

    app.register_blueprint(views, url_prefix="/")
    app.register_blueprint(auth, url_prefix="/")
  
    from .dbs import User
    from .dbs import UrlReference
    from .dbs import RefFolders
 
    db_create(app)
 
    # Login manager
  
    login_manager= LoginManager()
    login_manager.login_view = 'views.home'
    login_manager.init_app(app)
  
    # Searching and loading user
  
    @login_manager.user_loader
    def load_user(id):
        return User.query.get(int(id))
   
    return app
 
def db_create(app):
    if not path.exists("project/" + DB_NAME):
        db.create_all(app=app)

我不知道发生了什么，可能是双外键有问题？

Answer 1

我认为 flask 或其扩展可以猜测你想要的 table 名称，如 CamelCase --> camel_case.

所以在这种情况下，table名称可能是 ref_folders。您可能只想使用 tablename 自己设置 table 名称，尽管我认为它们的默认值是一个很好的约定。

作为旁注，我建议您使用 _id 作为您的 ID，否则对象关系和实际 ID 之间的事情可能会变得非常混乱，即。在 RefFolders.

中使用 user_id 而不是 user_rel

参见：

https://flask-sqlalchemy.palletsprojects.com/en/2.x/models/#declaring-models

Some parts that are required in SQLAlchemy are optional in Flask-SQLAlchemy. For instance the table name is automatically set for you unless overridden. It’s derived from the class name converted to lowercase and with “CamelCase” converted to “camel_case”. To override the table name, set the __tablename__ class attribute.

Sql 炼金术 sqlalchemy.exc.NoReferencedTableError 没有创建表格

Sql alchemy sqlalchemy.exc.NoReferencedTableError not creating tables

python

flask

sqlalchemy

flask-sqlalchemy