Python x和y之间无ForeignKeys错误
运行这两条线路:Python x和y之间无ForeignKeys错误,python,sqlalchemy,Python,Sqlalchemy,运行这两条线路: Base = declarative_base() class Database: def __init__(self): engine = create_engine('mysql+pymysql://...') self.session = sessionmaker(bind=engine)() Base.metadata.create_all(engine) print(engine.connec
Base = declarative_base()
class Database:
def __init__(self):
engine = create_engine('mysql+pymysql://...')
self.session = sessionmaker(bind=engine)()
Base.metadata.create_all(engine)
print(engine.connect().execute(
'Select * From Customer LEFT JOIN CustomerContact On Customer.ID = CustomerContact.CustomerID')
.fetchall())
class Customer(Base):
__tablename__ = 'Customer'
ID = Column(String, primary_key=True)
Name = Column(String)
contacts = relationship('CustomerContact')
class CustomerContact(Base):
__tablename__ = 'CustomerContact'
ID = Column(Integer, primary_key=True)
CustomerID = (String, ForeignKey('Customer.ID'))
Name = Column(String)
Title = Column(String, default='')
ContactInfo = Column(String, default='')
Notes = Column(String, default='')
if __name__ == '__main__':
db = Database()
s = db.session
s.query(Customer)
导致
session.query(Customer).all()
session.query(Customer).join(CustomerContact).all()
此外,查询与这两个类相关的任何内容似乎都会抛出这些错误
我已经检查了打字错误和其他线程,并运行了一个原始sql语句,看看其他地方是否有问题,但它工作得非常好
我当时正在学习这个例子
难道我一辈子都不知道到底是什么错了吗
如果有人能帮我指出正确的方向来进一步解决这个问题或问题所在,那将是令人惊讶的。您应该在选择中引用外键 而不是:
sqlalchemy.exc.NoForeignKeysError: Can't find any foreign key relationships
between 'Customer' and 'CustomerContact'.
尝试:
忘记在上调用Column()
谢谢你Ilja Everilä SQLAlchemy应该能够自动使用现有的外键关系,因此这里还有其他问题。此外,
CustomerContact.CustomerID==Customer.contacts
生成了一个相当时髦的ON子句:ON“CustomerContact”。“CustomerID=”(“Customer”。“ID”=“CustomerContact”。“CustomerID”)
,可能是因为Customer.contacts
是如何被改编的。您做了一个简单的输入:CustomerID=(字符串,ForeignKey('Customer.ID'))
将一个2元组指定为CustomerID
。你想创建一个专栏。哦,天哪,我真不敢相信我错过了!谢谢你的帮助!
session.query(Customer).join(CustomerContact).all()
session.query(Customer).join(CustomerContact, CustomerContact.CustomerID==Customer.contacts).all()
CustomerID = (String, ForeignKey('Customer.ID'))