关联查询 join的使用

Posted 2020-09-05 失落的黎明

 1 #!/usr/bin/env python
 2 import sqlalchemy
 3 from sqlalchemy import create_engine
 4 from sqlalchemy.ext.declarative import declarative_base
 5 from sqlalchemy import Column, Integer, String,ForeignKey
 6 from sqlalchemy.orm import sessionmaker,relationship
 7 print(sqlalchemy.__version__)
 8 
 9 engine = create_engine(‘mysql+pymysql://root:[email protected]:3306/a1‘,echo = True)
10 
11 Base = declarative_base(engine)
12 
13 class Father(Base):
14     __tablename__ = "father"
15 
16     id = Column(Integer,autoincrement=True,primary_key=True)
17     name = Column(String(20))
18     son = relationship(‘Father‘)
19     def __repr__(self):
20         return self.name
21 
22 class Son(Base):
23     __tablename__ = ‘son‘
24     id = Column(Integer,autoincrement=True,primary_key=True)
25     name = Column(String(20))
26     email = Column(String(20))
27     father_id = Column(Integer,ForeignKey(‘father.id‘))
28 Base.metadata.create_all(engine)
29 
30 Session = sessionmaker(bind=engine)
31 session = Session()
32 # f1 = Father(name = "fafafa")
33 # session.add(f1)
34 # s1 = Son(name = ‘sq‘,email = ‘@qq.com‘,father_id = 1)
35 # s2 = Son(name = ‘sw‘, email= ‘[email protected]‘,father_id= 1)
36 # session.add_all([s1,s2])
37 
38 
39 ret = session.query(Father.name,Son.name).join(Son).first()
40 print("ret=",ret)
41 session.commit()