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do_sqlalchemy.py
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do_sqlalchemy.py
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#!/bin/env python3
# -*- coding:utf-8 -*-
# python中的数据库DB-API返回的数据结构
'''
[
('1', 'Michael'),
('2', 'Bob'),
('3', 'Adam')
]
'''
# 用class实例表示
# 把关系数据库的表结构映射到对象上,即Object-Relational Mapping
# ORM框架
'''
class User(object):
def __init__(self, id, name):
self.id = id
self.name = name
[
User('1', 'Michael'),
User('2', 'Bob'),
User('3', 'Adam')
]
'''
# python 中的ORM框架SQLAlchemy
#
# 导入:
from sqlalchemy import Column, String, create_engine
from sqlalchemy.orm import sessionmaker
from sqlalchemy.ext.declarative import declarative_base
# 创建对象的基类:
Base = declarative_base()
# 定义User对象:
class User(Base):
# 表的名字:
__tablename__ = 'user'
# 表的结构:
id = Column(String(20), primary_key=True)
name = Column(String(20))
# 初始化数据库连接:str
engine = create_engine('mysql+mysqlconnector://root:password@localhost:3306/test')
# 创建DBSession类型:
DBSession = sessionmaker(bind=engine)
# 有了ORM框架,添加记录可视为添加User对象
# DBSession对象可视为当前数据库连接
# 创建session对象:
session = DBSession()
# 创建新User对象:
new_user = User(id='5', name='Bob')
# 添加到session:
session.add(new_user)
# 提交即保存到数据库:
session.commit()
# 关闭session:
session.close()
# 查询User对象
# 创建Session:
session = DBSession()
# 创建Query查询,filter是where条件,最后调用one()返回唯一行,如果调用all()则返回所有行:
user = session.query(User).filter(User.id=='5').one()
# 打印类型和对象的name属性:
print('type:', type(user))
print('name:', user.name)
# 关闭Session:
session.close()
# 定义关系
class User(Base):
__tablename__ = 'user'
id = Column(String(20), primary_key=True)
name = Column(String(20))
# 一对多:
books = relationship('Book')
class Book(Base):
__tablename__ = 'book'
id = Column(String(20), primary_key=True)
name = Column(String(20))
# “多”的一方的book表是通过外键关联到user表的:
user_id = Column(String(20), ForeignKey('user.id'))