004-sqlalchemy-Python_sqlalchemy实现简单的多对多数据表的创建

1 建立数据表

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

# charset=utf8 支持中文
engine = create_engine("mysql+pymysql://Jim:123456@localhost/testdb?charset=utf8",
                       encoding="utf-8", echo=True)
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 Author(Base):
    __tablename__ = "authors"
    name = Column(String(32),nullable=False)
    id = Column(Integer,primary_key=True)
    # books = relationship("Book",secondary=book_m2m_author,backref="authors")  #,back_ref="authors"

    def __repr__(self):
        return "name:%s" %self.name

class Book(Base):
    __tablename__ = "books"
    id = Column(Integer,primary_key=True)
    name = Column(String(32),nullable=False)
    pub_date = Column(DATE,nullable=False)
    authors = relationship("Author",secondary=book_m2m_author,backref="books")

    def __repr__(self):
        return "name:%s authors:%s" %(self.name,self.authors)

# Mapper(Book,book_m2m_author)
Base.metadata.create_all(bind=engine)

2 添加数据并查看

from sqlalchemy.orm import sessionmaker
import mysql_m2m

Session_class = sessionmaker(bind=mysql_m2m.engine)
session = Session_class()

b1 = mysql_m2m.Book(name="hello",pub_date="2011-02-9")
b2 = mysql_m2m.Book(name="world",pub_date="2011-03-9")
b3 = mysql_m2m.Book(name="roal",pub_date="2011-08-9")

a1 = mysql_m2m.Author(name="Jim")
a2 = mysql_m2m.Author(name="Tom")
a3 = mysql_m2m.Author(name="Mary")

b1.authors = [a1,a3]
b2.authors = [a2,a1,a3]

# session.add_all([b1,b2])

author_obj = session.query(mysql_m2m.Author).filter(mysql_m2m.Author.name=="Jim").first()
print(author_obj.name,author_obj.books)
book_obj = session.query(mysql_m2m.Book).filter(mysql_m2m.Book.id==3).first()
print(book_obj.authors,book_obj.name,book_obj.pub_date)
# book_obj.authors.remove(author_obj)
session.commit()