python sqlalchemy外键关联和多外键关联

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

engine = create_engine("mysql+pymysql://root:123456@192.168.181.128/ltest",
                       encoding='utf-8', echo=False)#类似于pymysql 的connect，echo等于True要刷日志

Base = declarative_base()  # 生成orm基类，定义一个实例，所有表必须继承该实例


class Student(Base):
    __tablename__ = 'student'
    id = Column(Integer,primary_key=True)
    name = Column(String(32),nullable=False)
    register_date =Column(DATE,nullable=False)


    def __repr__(self):
        return "<name(name='%s')>"%self.name

class StudyRecord(Base):
    __tablename__ = "study_record"
    id = Column(Integer,primary_key=True)
    day = Column(Integer,nullable=False)#nullable是不能为空
    status =Column(String(32),nullable=False)
    stu_id = Column(Integer,ForeignKey("student.id"))

    student = relationship("Student", backref="my_study_record") #这个nb，允许你在user表里通过backref字段反向查出所有它在addresses表里的关联项
    # student = query(Student).filter(Student.id == stu_obj.stu_id).first() relationship另一种介绍

    def __repr__(self):
        return "<%s day :%s  status %s>" % (self.student.name,self.day,self.status)

Base.metadata.create_all(engine)  # 创建表结构

#show create tables  study_record; 查询表结构

Session_class = sessionmaker(bind=engine)  # 创建与数据库的会话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,类似于pymysql的cursor

#插入数据
# s1 = Student(name="Anne",register_date="2014-05-21")
# s2 = Student(name="Jack",register_date="2015-05-21")
# s3 = Student(name="Rain",register_date="2016-05-21")
# s4 = Student(name="Eric",register_date="2017-05-21")
#
#
# study_obj1 = StudyRecord(day=1,status="YES",stu_id=1)
# study_obj2 = StudyRecord(day=2,status="NO",stu_id=1)
# study_obj3 = StudyRecord(day=3,status="YES",stu_id=1)
# study_obj4 = StudyRecord(day=1,status="YES",stu_id=1)
# study_obj5 = StudyRecord(day=4,status="YES",stu_id=2)

# session.add_all([s1,s2,s3,s4,study_obj1,study_obj2,study_obj3,study_obj4,study_obj5])


stu_obj = session.query(Student).filter(Student.name=="Anne").first()
print(stu_obj.my_study_record)
session.commit()

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

Base = declarative_base()
engine = create_engine("mysql+pymysql://root:123456@192.168.181.128/ltest",
                       encoding='utf-8', echo=False)#类似于pymysql 的connect，echo等于True要刷日志

class Customer(Base):
    __tablename__ = 'customer'
    id = Column(Integer, primary_key=True)
    name = Column(String(64))

    billing_address_id = Column(Integer, ForeignKey("address.id"))
    shipping_address_id = Column(Integer, ForeignKey("address.id"))

    billing_address = relationship("Address",foreign_keys=[billing_address_id])
    shipping_address = relationship("Address",foreign_keys=[shipping_address_id])


class Address(Base):
    __tablename__ = 'address'
    id = Column(Integer, primary_key=True)
    street = Column(String(64))
    city = Column(String(64))
    state = Column(String(64))

    def __repr__(self):
        return self.street


Base.metadata.create_all(engine)  # 创建表结构

from practice import orm_Multiple_foreign_keys

from sqlalchemy.orm import sessionmaker

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

#创建
# addr1 = orm_Multiple_foreign_keys.Address(street="tiankonggyuan",city="Pudongxinqu",state = "shang hai")
# addr2 = orm_Multiple_foreign_keys.Address(street="yananxilu",city="Changling",state = "shang hai")
# addr3 = orm_Multiple_foreign_keys.Address(street="tiananmen",city="Chaoyangqu",state = "Bei jing")
#
# session.add_all([addr1,addr2,addr3])
# c1 = orm_Multiple_foreign_keys.Customer(name="Anne",billing_address=addr1,shipping_address=addr2)
# c2 = orm_Multiple_foreign_keys.Customer(name="Jack",billing_address=addr3,shipping_address=addr3)
#
# session.add_all([c1,c2])

obj =session.query(orm_Multiple_foreign_keys.Customer).filter(orm_Multiple_foreign_keys.Customer.name == "Anne").first()
print(obj.name,obj.billing_address,obj.shipping_address)
session.commit()

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

Base = declarative_base()
engine = create_engine("mysql+pymysql://root:123456@192.168.181.128/ltest",
                       encoding='utf-8', echo=False)#类似于pymysql 的connect，echo等于True要刷日志

#创建表
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))
    pud_date = Column(DATE)
    authors = relationship('Author',secondary = book_m2m_author,backref = 'books')#secondary 查询第3张表关联，反向去查询

    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


Base.metadata.create_all(engine)

session_class = sessionmaker(bind=engine)
session = session_class()

# b1 = Book(name="跟Anne学Python")
# b2 = Book(name="跟Anne学把妹")
# b3 = Book(name="跟Anne学装逼")
# b4 = Book(name="跟Anne学开车")
#
# a1 = Author(name="Anne")
# a2 = Author(name="Jack")
# a3 = Author(name="Rain")
#
#
# b1.authors = [a1,a2]
# b2.authors = [a1,a2,a3]
#
# session.add_all([b1,b2,b3,b4,a1,a2,a3])
# session.commit()

print('--------通过书表查关联的作者---------')

book_obj = session.query(Book).filter_by(name="跟Anne学Python").first()
print(book_obj.name, book_obj.authors)

print('--------通过作者表查关联的书---------')
author_obj = session.query(Author).filter_by(name="Anne").first()
print(author_obj.name, author_obj.books)
session.commit()


#通过书删除作者
author_obj = session.query(Author).filter_by(name="Jack").first()
book_obj = session.query(Book).filter_by(name="跟Anne学把妹").first()
book_obj.authors.remove(author_obj)  # 从一本书里删除一个作者
session.commit()

#直接删除作者
author_obj =session.query(Author).filter_by(name="Anne").first()
session.delete(author_obj)
session.commit()

处理中文

sqlalchemy设置编码字符集一定要在数据库访问的URL上增加charset=utf8，否则数据库的连接就不是utf8的编码格式

eng = create_engine('mysql://root:root@localhost:3306/test2?charset=utf8',echo=True)

relationship的使用：使两个表之间产生管理，类似于合成一张表，可以直接取出关联的表，进行获取数据，而不需要join操作