automap

Posted 2020-08-28 台灯不太亮

一、事先定义的表结构

• db_init.py

#!/usr/bin/env python
# -*- coding:utf-8 -*-

from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, Boolean
from sqlalchemy import ForeignKey
from sqlalchemy.orm import relationship
from sqlalchemy.orm import sessionmaker

engine = create_engine("mysql+pymysql://root:[email protected]/db01?charset=utf8")
Base = declarative_base()

class Student(Base):
    __tablename__ = ‘student‘
    id = Column(Integer, primary_key=True)
    name = Column(String(32), nullable=False)
    address = relationship(‘Address‘, backref=‘student‘)

class Address(Base):
    __tablename__ = ‘address‘
    id = Column(Integer, primary_key=True)
    u_id = Column(Integer, ForeignKey(‘student.id‘))
    name = Column(String(32), nullable=False)

# Base.metadata.drop_all(bind=engine)
Base.metadata.create_all(bind=engine)

session_cls = sessionmaker(bind=engine)
session = session_cls()

session.add_all([
    Student(name=‘user1‘),
    Student(name=‘user2‘),
    Student(name=‘user3‘),
    Address(u_id=1, name=‘add-1‘),
    Address(u_id=2, name=‘add-2‘),
    Address(u_id=3, name=‘add-3‘),
    Address(u_id=3, name=‘add-4‘),
])
# session.commit()
# 利用 backref查找，成功
ret = session.query(Address).filter(Address.u_id == 1).first().student.name
print(ret)

二、不知道表结构

• automap.py   # 注意，此处只是一对多，反射到了releastionsip，多对多没有测试成功，但是官网说可以

#!/usr/bin/env python
# -*- coding:utf-8 -*-

import random
from sqlalchemy.ext.automap import automap_base
from sqlalchemy.orm import Session
from sqlalchemy.orm import relationship
from sqlalchemy import create_engine

# 初始化一个automap类
Base = automap_base()
engine = create_engine("mysql+pymysql://root:[email protected]/db01?charset=utf8")
Base.prepare(engine, reflect=True)  # 反射所有的表

session = Session(engine)
Student = Base.classes.student  # 获取所需要的表
Address = Base.classes.address

# 利用表的backref 成功获取结果
ret = session.query(Address).filter(Address.u_id == 1).first().student.name
print(ret)