如何自动将数据库反映为sqlalchemy声明式？

好吧，我经历了一下，尝试在Northwind数据库上尝试，它看起来很有希望。虽然，我必须添加关系字段才能跟踪数据库关系。

让我们考虑一下，在启动应用程序时我不知道表之间的关系，因此我需要一种自动生成的方法。

import unittestfrom sqlalchemy import *from sqlalchemy.orm import create_sessionfrom sqlalchemy.ext.declarative import declarative_basefrom datetime import datetimefrom sqlalchemy.orm import contains_eager, joinedloadfrom sqlalchemy.orm import relationship#Create and engine and get the metadatabase = declarative_base()engine = create_engine('mssql://user:pass@Northwind', echo=True)metadata = metaData(bind=engine)#Reflect each database table we need to use, using metadataclass Customer(base):    __table__ = Table('Customers', metadata, autoload=True)    orders = relationship("Order", backref="customer")class Shipper(base):    __table__ = Table('Shippers', metadata, autoload=True)    orders = relationship("Order", backref="shipper")class Employee(base):    __table__ = Table('Employees', metadata, autoload=True)#    orders = relationship("Order", backref="employee")    territories = relationship('Territory', secondary=Table('Employeeterritories', metadata, autoload=True))class Territory(base):    __table__ = Table('Territories', metadata, autoload=True)    region = relationship('Region', backref='territories')class Region(base):    __table__ = Table('Region', metadata, autoload=True)class Order(base):    __table__ = Table('Orders', metadata, autoload=True)    products = relationship('Product', secondary=Table('Order Details', metadata, autoload=True))    employee = relationship('Employee', backref='orders')class Product(base):    __table__ = Table('Products', metadata, autoload=True)    supplier = relationship('Supplier', backref='products')    category = relationship('Category', backref='products')class Supplier(base):    __table__ = Table('Suppliers', metadata, autoload=True)class Category(base):    __table__ = Table('Categories', metadata, autoload=True)class Test(unittest.TestCase):    def setUp(self):        #Create a session to use the tables self.session = create_session(bind=engine)    def tearDown(self):        self.session.close()    def test_withJoins(self):        q = self.session.query(Customer)        q = q.join(Order)        q = q.join(Shipper)        q = q.filter(Customer.CustomerID =='ALFKI')        q = q.filter(Order.OrderID=='10643')        q = q.filter(Shipper.ShipperID=='1')        q = q.options(contains_eager(Customer.orders, Order.shipper))        res = q.all()        cus = res[0]        ord = cus.orders[0]        shi = ord.shipper        self.assertEqual(shi.Phone, '(503) 555-9831')