关联查询 join的使用

 #!/usr/bin/env python
 import sqlalchemy
 from sqlalchemy import create_engine
 from sqlalchemy.ext.declarative import declarative_base
 from sqlalchemy import Column, Integer, String,ForeignKey
 from sqlalchemy.orm import sessionmaker,relationship
 print(sqlalchemy.__version__)

 engine = create_engine('mysql+pymysql://root:taochen123@127.0.0.1:3306/a1',echo = True)

 Base = declarative_base(engine)

 class Father(Base):
     __tablename__ = "father"

     id = Column(Integer,autoincrement=True,primary_key=True)
     name = Column(String(20))
     son = relationship('Father')
     def __repr__(self):
         return self.name

 class Son(Base):
     __tablename__ = 'son'
     id = Column(Integer,autoincrement=True,primary_key=True)
     name = Column(String(20))
     email = Column(String(20))
     father_id = Column(Integer,ForeignKey('father.id'))
 Base.metadata.create_all(engine)

 Session = sessionmaker(bind=engine)
 session = Session()
 # f1 = Father(name = "fafafa")
 # session.add(f1)
 # s1 = Son(name = 'sq',email = '@qq.com',father_id = 1)
 # s2 = Son(name = 'sw', email= 'q@qq.com',father_id= 1)
 # session.add_all([s1,s2])

 ret = session.query(Father.name,Son.name).join(Son).first()
 print("ret=",ret)
 session.commit()