SQLAlchemy学习笔记(外键,关联) 3

下面是数据库关联

1. 一对多(一个User可以有多个Address)
   ①建立外键 一对多关系
   

   class User(Base):
   	__tablename__ = "users"
   	id = Column(Integer, Sequence("user_id_seq"), primary_key=True)
           # ...
   	addresses = relationship("Address", backref="user", order_by="Address.id") # User中有addresses字段
           # ...
   
   class Address(Base):
       # ...
       id = Column(Integer, primary_key=True)
       user_id = Column(Integer, ForeignKey("users.id")) # Address表的外键是User表的主键 多个Address属于一个User(多对一)
       # ...

   下面是完整代码

   # -*- coding: utf-8 -*-
   
   from sqlalchemy import Column, Sequence, String, Integer, ForeignKey
   from sqlalchemy import create_engine # 导入创建连接驱动
   from sqlalchemy.ext.declarative import declarative_base
   from sqlalchemy.orm import sessionmaker
   from sqlalchemy.orm import relationship, backref
   
   engine = create_engine("mysql://root:[email protected]/test", echo=True) # 这个url可以用urlparse解析, 其中echo=True表示执行时显示sql语句
   Base = declarative_base() # 生成了declarative基类, 以后的model继承此类
   
   class User(Base):
   	__tablename__ = "users"
   	id = Column(Integer, Sequence("user_id_seq"), primary_key=True) # Sequence表示id自增长, 主键
   	name = Column(String(50))
   	fullname = Column(String(50))
   	password = Column(String(12))
   	addresses = relationship("Address", backref="user", order_by="Address.id")
   
   	def __init__(self, name, fullname, password):
   		self.name = name
   		self.fullname = fullname
   		self.password = password
   
   	def __repr__(self):
   		return "<User('%s', '%s', '%s')>" % (self.name, self.fullname, self.password)
   
   class Address(Base):
       __tablename__ = "addresses"
       id = Column(Integer, primary_key=True)
       email_address = Column(String(50), nullable=False)
       user_id = Column(Integer, ForeignKey("users.id")) # Address表的外键是User表的主键 多个Address属于一个User(多对一)
       user = relationship("User", backref=backref("addresses", order_by=id))
       
       def __init__(self, email_address):
           self.email_address = email_address
           
       def __repr__(self):
           return "<Address('%s')>" % self.email_address  Base.metadata.create_all(engine)
   

   ②使用

   Session = sessionmaker(bind=engine) # 创建一个Session类
   session = Session() # 生成一个Session实例
                            
   zhangsan = User("zs", "zhangsan", "abcdef")
   zhangsan.addresses = [
           Address(email_address="[email protected]"),
           Address(email_address="[email protected]"),
           ]
   
   session.add(zhangsan)
   session.commit()

   ③下面对应的sql语句

   CREATE TABLE users (
   	id INTEGER NOT NULL AUTO_INCREMENT, 
   	name VARCHAR(50), 
   	fullname VARCHAR(50), 
   	password VARCHAR(12), 
   	PRIMARY KEY (id)
   )
   
   CREATE TABLE addresses (
   	id INTEGER NOT NULL AUTO_INCREMENT, 
   	email_address VARCHAR(50) NOT NULL, 
   	user_id INTEGER, 
   	PRIMARY KEY (id), 
   	FOREIGN KEY(user_id) REFERENCES users (id)
   )