#!-*-coding:utf-8-*-
from sqlalchemy import Table,Column,Integer,String,DATE,ForeignKey
from sqlalchemy.orm import relationship
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
base=declarative_base()
book_m2m_author=Table('book_m2m_author',base.metadata,
Column('book_id',Integer,ForeignKey('books.id')),
Column('author_id',Integer,ForeignKey('authors.id')))
class Book(base):
__tablename__='books'
id=Column(Integer,primary_key=True)
name=Column(String(64))
pub_date=Column(DATE)
authors=relationship("Author",secondary=book_m2m_author,backref='books')#secondary查第三张表关联关系 backref Author反查有多少本书
def __repr__(self):
return self.name
class Author(base):
__tablename__='authors'
id=Column(Integer,primary_key=True)
name=Column(String(32))
def __repr__(self):
return self.name
engine=create_engine("mysql+pymysql://root:[email protected]/shop_db?charset=utf8",echo=False)#连接数据库 echo=TRUE输出执行过程
#?charset=utf8可插入汉字
base.metadata.create_all(engine)#创建表
sqlalchemy_many_to_many_api.py
from day12 import sqlalchemy_many_to_mang
from sqlalchemy.orm import sessionmaker
Session_class = sessionmaker(bind=sqlalchemy_many_to_mang.engine) # 创建与数据库的连接session class ,注意,这里返回给session的是个class,不是实例
session = Session_class() # 生成session实例 session会话 类似cursor
'''
b1=sqlalchemy_many_to_mang.Book(name="leran python with Alex",pub_date="2017-06-25")
b2=sqlalchemy_many_to_mang.Book(name="leran zhangbility with alex",pub_date="2016-06-25")
b3=sqlalchemy_many_to_mang.Book(name="leran hook uo girls with alex",pub_date="2015-06-25")
b4=sqlalchemy_many_to_mang.Book(name="风萧萧兮易水寒",pub_date="2018-06-25")
a1=sqlalchemy_many_to_mang.Author(name="alex")
a2=sqlalchemy_many_to_mang.Author(name="jack")
a3=sqlalchemy_many_to_mang.Author(name="rain")
b1.authors=[a1,a3]
b3.authors=[a1,a2,a3]
session.add_all([b4])
'''
author_obj=session.query(sqlalchemy_many_to_mang.Author).filter(sqlalchemy_many_to_mang.Author.name=="alex").first()
print(author_obj.books)#通过作者取书
book_obj=session.query(sqlalchemy_many_to_mang.Book).filter(sqlalchemy_many_to_mang.Book.id==2).first()
print(book_obj.authors)
#book_obj.authors.remove(author_obj)#给书删除作者
#session.delete(author_obj)#删除作者
session.commit()