Python 学习笔记 - SQLAlchemy(下)
from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index,Table
from sqlalchemy.orm import sessionmaker, relationship
engine = create_engine("mysql+pymysql://yli:yli@sydnagios:3306/mydb", max_overflow=5)
Base = declarative_base()
class HostToHostUser(Base):
__tablename__ = 'host_to_host_user'
nid = Column(Integer, primary_key=True,autoincrement=True)
host_id = Column(Integer ,ForeignKey('host.nid'))
host_user_id = Column(Integer, ForeignKey('host_user.nid'))
#配置关系
host = relationship("Host", backref='h')
host_user = relationship("HostUser", backref='u')
class Host(Base): # metaclass,Host.table对象
__tablename__ = 'host'
nid = Column(Integer, primary_key=True,autoincrement=True)
hostname = Column(String(32))
port = Column(String(32))
ip = Column(String(32))
class HostUser(Base):
__tablename__ = 'host_user'
nid = Column(Integer, primary_key=True,autoincrement=True)
username = Column(String(32))
#def init_db():
# Base.metadata.create_all(engine)
#
# def drop_db():
# Base.metadata.drop_all(engine)
#init_db()
Session = sessionmaker(bind=engine)
session = Session()
host_obj = session.query(Host).filter(Host.hostname=='c1').first()
print(host_obj.nid)
print(host_obj.hostname)
# 第三表对应的对象（逆向查询）
print(host_obj.h)
# 循环获取的第三表对应的对象
for item in host_obj.h:
print(item.host_user,item.host_user.nid,item.host_user.username)
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"C:\Program Files\Python3\python.exe" "C:/Users/yli/Documents/Tencent Files/38144205/FileRecv/s13课上代码/s13课上代码/s13day13课上代码/s13day13_课上代码/ORM—de,p.py"
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c1
[, , ]
1 root
2 db
3 nb
Process finished with exit code 0
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