創建表時Sqlalchemy外鍵關系錯誤

Question

我使用 sqlalchemy 創建表，其中一些表有多個外鍵關系。下面是代碼。 我收到錯誤：

sqlalchemy.exc.NoForeignKeysError：找不到“項目”和“流派”之間的任何外鍵關系

嘗試運行腳本時。

任何人都可以向我解釋如何在 sqlalchemy 中創建表，如果表具有多個關系，則創建順序。

   import sqlalchemy
   from  sqlalchemy.orm import *
   from sqlalchemy.ext.declarative import declarative_base
   import datetime
   from sqlalchemy import *


   engine =               sqlalchemy.create_engine('postgresql+psycopg2://postgres:newpassword@localhost:5432/test');


   Session = sessionmaker(bind=engine)


   session = Session()

   metadata = MetaData(engine)


   metadata.drop_all(engine)

   Base = declarative_base(metadata=metadata)

   class User(Base):
        __tablename__ = 'users'
        id = Column(Integer,primary_key = True)
        email = Column(String(30),nullable = False)
        password = Column(String(30),nullable = False)

   class Genre(Base):
        __tablename__ = 'genre'
        id = Column(Integer,primary_key = True)
        title = Column(String(30),nullable = False)

   class Status(Base):
        __tablename__ = 'status'
        id = Column(Integer,primary_key = True)
        status = Column(String(30),nullable = False)

   class FilmType(Base):
        __tablename__ = 'filmtype'
        id = Column(Integer,primary_key = True)
        filmtype = Column(String(30),nullable = False)

   class Project(Base):
        __tablename__ = 'project'
        id = Column(Integer,primary_key = True)
        name = Column(String(30),nullable = False)
        poster = Column(Text, nullable = False)
        genre_id = Column(Integer,ForeignKey('genre.id'))
        genre_id = relationship('Genre',backref = 'genres')
        owner = Column(Integer,ForeignKey('users.id'))
        owner = relationship('Users',backref = 'users')


   class Videos(Base):
         __tablename__ = 'videos'
         id = Column(Integer,primary_key = True)
         dropbox_url = Column(Text)
         film_type = Column(Integer,ForeignKey('filmtype.id'))
         film_type = relationship('FilmType',backref = 'film_types')
         video_status = Column(Integer,ForeignKey('status.id'))
         video_status = relationship('Status',backref = 'video_statuses')
         project_id = Column(Integer,ForeignKey('project.id'))
         project_id = relationship('Project',backref = 'projetcs')
         user_id = Column(Integer,ForeignKey('users.id'))
         user_id = relationship('User', backref = 'video_owners')


  metadata.create_all(bind = engine)
  user_ = User(email='lala.com',password='lala')
  genre_ = Genre(title='Horror')
  status_ = Status(status='Active')
  filmtype_ = FilmType(filmtype ='lala')
  project_ = Project(name='lala',poster='mij.jpg')
  videos_ = Videos(dropbox_url='drop/vi.com')
  session.add(videos_)
  session.flush()
  session.commit()

錯誤

“sqlalchemy.exc.NoForeignKeysError：無法確定關系Project.genre_id的父/子表之間的連接條件> - 沒有鏈接這些表的外鍵。確保引用列與ForeignKey或ForeignKeyConstraint相關聯，或指定'primaryjoin ' 表達。”

Answer 1

您正在用關系對象覆蓋列規范，因此 SQLAlchemy 永遠不會看到這些列。 查看您的數據庫是否在表中沒有外鍵列，並將列或關系類變量重命名為具有唯一名稱。 也許是這樣的：

owner_id = Column(Integer,ForeignKey('users.id'))
owner = relationship('Users',backref = 'users')

Answer 2

就我而言，我寫了表格但忘記了列：

owner_id = Column(Integer, ForeignKey('users'))

代替

owner_id = Column(Integer, ForeignKey('users.id'))