Flask中的的SQLAlchemy2

from sqlalchemy import Column,Integer,String,ForeignKey
from sqlalchemy.orm import relationship
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()

class Girls(Base):
    __tablename__ = ‘girl‘
    id = Column(Integer,primary_key=True)
    name = Column(String(32))
    #表的关系
    girl2boy = relationship("Boys",secondary = "hotel",backref = "boy2girl")

class Boys(Base):
    __tablename__ = ‘boy‘
    id = Column(Integer,primary_key=True)
    name = Column(String(32))


class Hotel(Base):
    __tablename__=‘hotel‘
    id = Column(Integer,primary_key=True)
    girl_id = Column(Integer,ForeignKey("girl.id"))
    boy_id = Column(Integer,ForeignKey("boy.id"))

from sqlalchemy import create_engine
#这里不懂得，戳紫色的字！！
engine = create_engine("mysql+pymysql://root:614615@127.0.0.1:3306/day127?charset=utf8")

Base.metadata.create_all(engine)

#curd_M2M.py

from sqlalchemy.orm import sessionmaker
from SQL.curd_M2m import engine
from SQL.curd_M2m import Boys,Girls,Hotel
Session = sessionmaker(engine)
db_session = Session()

#t通过想Boy添加数据添加girl和hotel数据。relationship反向
boy = Boys(name="李志强")
boy.boy2girl = [Girls(name="哇哈哈"),Girls(name="喜洋洋")]
db_session.add(boy)
db_session.commit()
db_session.close()


#t通过想Girl添加数据添加boy和hotel数据。relationship正向
girl_obj = Girls(name="李二短",girl2boy=[Boys(name="任二狗"),Boys(name="任梦")])
db_session.add(girl_obj)
db_session.commit()
db_session.close()



# 查询 正向查询
ret = db_session.query(Girls).all()
for girl in ret:
    for boy in girl.girl2boy:
#这里说一下，注意表的结构，有很多的小的细节不注意就会报错，查到girl信息，再次遍历的时候注意girl.girl2boy，正向查询
        print(girl.name , boy.name)

# 查询 反向查询
ret = db_session.query(Boys).all()
for boy in  ret:
    for girl in boy.boy2girl:
        print(boy.name,girl.name)