?多外鍵關聯

注：在兩個表之間進行多外鍵鏈接

?

如圖：

?

案例：

# 創建兩張表并添加外鍵主鍵

# 調用Column創建字段 加類型 from sqlalchemy import Integer, ForeignKey, String, Column# 調用基類Base from sqlalchemy.ext.declarative import declarative_base# 調用操作鏈接,反查 from sqlalchemy.orm import relationship# 調用鏈接數據庫 from sqlalchemy import create_engineBase = declarative_base()class Customer(Base):__tablename__ = 'customer'id = Column(Integer, primary_key=True)name = Column(String(64))# 以Address表id字段 設置兩個外鍵billing_address_id = Column(Integer, ForeignKey("address.id"))shipping_address_id = Column(Integer, ForeignKey("address.id"))# relationship -允許你在Student表里通過backref字段反向查出所有它在表里的關聯項-# foreign_keys=綁定外鍵 多次relationship 反差會識別不出指定數據所以添加foreign_keys參數。billing_address = relationship("Address",foreign_keys=[billing_address_id])shipping_address = relationship("Address",foreign_keys=[shipping_address_id])class Address(Base):__tablename__ = 'address'id = Column(Integer, primary_key=True)street = Column(String(64))city = Column(String(64))state = Column(String(64))# 返回一個可以用來表示對象的可打印字符串def __repr__(self):return self.street# encoding='utf-8' 鏈接字符集 ，echo=True 把所有信息打印出來 engine = create_engine("mysql+pymysql://root:123456@192.168.1.100/xiang",encoding='utf-8',#echo=True )#---------------1.創建表-----------------# # 創建表結構 Base.metadata.create_all(engine) #---------------------------------------#

?

# 插入表內字段數據，測試訪問

from www import orm_fk from sqlalchemy.orm import sessionmaker# bind=engine 綁定engine socket實例 Session_class = sessionmaker(bind=orm_fk.engine)# 生成session實例，如同pymysql內的cursor Session = Session_class()#---------------2.寫入數據-----------------## 寫入數據 # addr1 = orm_fk.Address(street="Tiantongyuan",city="ChangPing",state="BJ") # addr2 = orm_fk.Address(street="Wudaokou",city="Haidian",state="BJ") # addr3 = orm_fk.Address(street="Yanjiao",city="Langfang",state="HB")# 插入數據 # Session.add_all([addr1,addr2,addr3])# 寫入數據 并調用 Address字段插入數據 為 Customer數據 # c1 = orm_fk.Customer(name="kevin",billing_address=addr1,shipping_address=addr2) # c2 = orm_fk.Customer(name="Jack",billing_address=addr3,shipping_address=addr3)# 插入數據 # Session.add_all([c1,c2]) #---------------------------------------##---------------3.查詢數據-----------------## 取出Customer內的 內存對象 obj = Session.query(orm_fk.Customer).filter(orm_fk.Customer.name=="kevin").first()# 通過內存 調用第一行name字段數據， # 調用billing_address對應外鍵id的對應數據， # 調用obj.shipping_address對應外鍵id的對應數據。 print(obj.name,obj.billing_address,obj.shipping_address) #---------------------------------------## 執行事務 Session.commit() # 表customer +----+-------+--------------------+---------------------+ | id | name | billing_address_id | shipping_address_id | +----+-------+--------------------+---------------------+ | 1 | kevin | 1 | 2 | | 2 | Jack | 3 | 3 | +----+-------+--------------------+---------------------+# 表address +----+--------------+-----------+-------+ | id | street | city | state | +----+--------------+-----------+-------+ | 1 | Tiantongyuan | ChangPing | BJ | | 2 | Wudaokou | Haidian | BJ | | 3 | Yanjiao | Langfang | HB | +----+--------------+-----------+-------+ 數據庫測試

?

轉載于:https://www.cnblogs.com/xiangsikai/p/8328430.html

總結

以上是生活随笔為你收集整理的Python sqlalchemy orm 多外键关联的全部內容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網站內容還不錯，歡迎將生活随笔推薦給好友。