Question

尝试使用db_create.py构建数据库时出现以下错误。根据文档，当你使用backref时，它应该向另一个类添加一个外键，但由于某种原因它不是。

错误：

sqlalchemy.exc.NoForeignKeysError: Could not determine join condition between parent/child tables on relationship Message.users - there are no foreign keys linking these tables.  Ensure that referencing columns are associated with a ForeignKey or ForeignKeyConstraint, or specify a 'primaryjoin' expression.

models.py

class Message(db.Model):
    id=db.Column(db.Integer, primary_key=True)
    message=db.Column(db.String(69), unique=True, nullable=False)
    timestamp=db.Column(db.DateTime)

    #Problem Code below
    users=db.relationship('Message_User', backref='message', lazy='dynamic')
    children=db.relationship('Message_Group', backref='message', lazy='dynamic')
    #group backrefs Group

class Message_User(db.Model):
    __tablename__='message_user'
    id=db.Column(db.Integer, primary_key=True)
    acknowledge=db.Column(db.DateTime, default=False)
    timestamp=db.Column(db.DateTime)
    #group backrefs Message_Group
    #message backrefs Message

db_createpy

#!flask/bin/python
from migrate.versioning import api
from config import SQLALCHEMY_DATABASE_URI
from config import SQLALCHEMY_MIGRATE_REPO
from app import db
import os.path
db.create_all()
if not os.path.exists(SQLALCHEMY_MIGRATE_REPO):
    api.create(SQLALCHEMY_MIGRATE_REPO, 'database repository')
    api.version_control(SQLALCHEMY_DATABASE_URI, SQLALCHEMY_MIGRATE_REPO)
else:
    api.version_control(SQLALCHEMY_DATABASE_URI, SQLALCHEMY_MIGRATE_REPO,
                        api.version(SQLALCHEMY_MIGRATE_REPO))

sqlalchemy中的foreignkey错误

0 个答案: