''' 对象关系映射（英语：(Object Relational Mapping，简称ORM，或O/RM，或O/R mapping），是一种程序技术，用于实现面向对象编程语言里不同类型系统的数据之间的转换 。 从效果上说，它其实是创建了一个可在编程语言里使用的--“虚拟对象数据库”。 ''' import sqlalchemy from sqlalchemy import create_engine from sqlalchemy.ext.declarative import declarative_base from sqlalchemy import Column,Integer,String from sqlalchemy.orm import sessionmaker from sqlalchemy import func #指定连接信息 #可以使用的连接类型 MySQL-Python,pymysql , MySQL-Connector,cx_Oracle engine= create_engine('mysql+pymysql://root:123@localhost/mydb',encoding='utf-8',echo=True) #生成ORM基类 Base=declarative_base() class User(Base): __tablename__='user2' #表名 #声明列 id = Column(Integer,primary_key=True,autoincrement=True) name=Column(String(32)) password = Column(String(64)) def __repr__(self): return "<%s name : %s>"%(self.id ,self.name) class Student(Base): __tablename__ = 'student' # 表名 # 声明列 id = Column(Integer, primary_key=True, autoincrement=True) name = Column(String(32)) def __repr__(self): return "<%s name : %s>" % (self.id, self.name) #创建表结构 Base.metadata.create_all(engine) '''与数据库交互''' #创建与数据库连接的会话 , 这里返回的是一个类 Session_class = sessionmaker(bind=engine) #生成 session 实例 Session = Session_class() # # user_obj = User(name='xiaowan',password='123456') # print(user_obj.name,user_obj.id) # # #将数据添加到session 中 # Session.add(user_obj) #查询,返回一个对象 #data = Session.query(User).filter(id>2).filter(id<5).all() data = Session.query(User).filter_by(id='1').first() print(data) #修改 # data.name='xiaoxiao' #统计数量 print(Session.query(User).filter(User.name.like("x%")).count() ) #分组统计 print(Session.query(func.count(User.name),User.name).group_by(User.name).all()) #回滚 # Session.rollback() #连接查询 print(Session.query(User,Student).filter(User.id ==Student.id).all()) #提交 Session.commit()
添加外键：
''' 外键 ''' import sqlalchemy from sqlalchemy import create_engine from sqlalchemy.ext.declarative import declarative_base from sqlalchemy import Column,Integer,String,ForeignKey from sqlalchemy.orm import sessionmaker,relationship from sqlalchemy import func #指定连接信息 #可以使用的连接类型 MySQL-Python,pymysql , MySQL-Connector,cx_Oracle engine= create_engine('mysql+pymysql://root:123@localhost/mydb',encoding='utf-8',echo=True) #生成ORM基类 Base=declarative_base() class Student(Base): __tablename__ = 'student' # 表名 # 声明列 id = Column(Integer, primary_key=True, autoincrement=True) name = Column(String(32)) def __repr__(self): return "<%s name : %s>" % (self.id, self.name) class StudyRecord(Base): __tablename__ = 'Study_record' id = Column(Integer, primary_key=True, autoincrement=True) day = Column(Integer,nullable=False) statrus = Column(String(32),nullable=False) #外键关联student id stu_id = Column(Integer,ForeignKey("student.id")) #添加一个关系 ,让StudyRecord可以调用student student = relationship("Student", backref="my_study_record") def __repr__(self): return "<%s day:%s status:%s>" % (self.student.name,self.day,self.statrus) #生成表结构 Base.metadata.create_all(engine) #创建与数据库连接的会话 , 这里返回的是一个类 Session_class = sessionmaker(bind=engine) #生成 session 实例 session = Session_class() # s1 = Student(name='aaa') # s2 = Student(name='bbb') # s3 = Student(name='ccc') # s4 = Student(name='ddd') # # obj1 = StudyRecord(day=1,statrus="Y",stu_id=1) # obj2 = StudyRecord(day=2,statrus="Y",stu_id=1) # obj3 = StudyRecord(day=3,statrus="Y",stu_id=1) # obj4 = StudyRecord(day=1,statrus="Y",stu_id=2) # 查询 stu_obj = session.query(Student).filter(Student.name=="aaa").first() print("---------------------") print(stu_obj.my_study_record) # session.add_all([s1,s2,s3,s4,obj1,obj2,obj3,obj4]) # session.commit()
多外键：
from sqlalchemy import Integer,ForeignKey,String,Column from sqlalchemy.ext.declarative import declarative_base from sqlalchemy.orm import relationship,sessionmaker from sqlalchemy import create_engine,ForeignKey Base = declarative_base() class Customer(Base): __tablename__='customer' id = Column(Integer,primary_key=True) name= Column(String(64)) #外键 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 engine= create_engine('mysql+pymysql://root:123@localhost/mydb',encoding='utf-8',echo=True) Base.metadata.create_all(engine) #创建与数据库连接的会话 , 这里返回的是一个类 Session_class = sessionmaker(bind=engine) #生成 session 实例 session = Session_class() # #插入数据 # # addr1 = Address(street="FT",city="fengtai",state="beijing") # addr2 = Address(street="CY",city="chaoyang",state="beijing") # addr3 = Address(street="PD",city="pudong",state="shanghai") # # session.add_all([addr1,addr2,addr3]) # # c1 = Customer(name="xiaoqiang",billing_address=addr1,shipping_address=addr2) # c2 = Customer(name="jack",billing_address=addr3,shipping_address=addr3) # # session.add_all([c1,c2]) #查询 obj = session.query(Customer).filter(Customer.name=="xiaoqiang").first() print(obj.name,obj.billing_address,obj.shipping_address) session.commit()
多对多关系：
from sqlalchemy import Integer,ForeignKey,String,Column,Table from sqlalchemy.ext.declarative import declarative_base from sqlalchemy.orm import relationship,sessionmaker from sqlalchemy import create_engine,ForeignKey Base = declarative_base() book_m2m_author = Table('book_m2m_author',Base.metadata, Column('book_id',Integer,ForeignKey('book.id')), Column('author_id',Integer,ForeignKey('author.id')) ) #book table class Book(Base): __tablename__='book' id = Column(Integer,primary_key=True) name = Column(String(64)) authors = relationship('Author',secondary=book_m2m_author ,backref='books') def __repr__(self): return self.name #Author table class Author(Base): __tablename__ = 'author' id = Column(Integer,primary_key=True) name= Column(String(64)) def __repr__(self): return self.name engine= create_engine('mysql+pymysql://root:123@localhost/mydb?charset=utf8',encoding='utf-8',echo=True) Base.metadata.create_all(engine) #创建与数据库连接的会话 , 这里返回的是一个类 Session_class = sessionmaker(bind=engine) #生成 session 实例 session = Session_class() # # #插入数据 # b1= Book(name='java') # b2= Book(name='c#') # b3= Book(name='python') b3 = Book(name='语文') # # # a1= Author(name='jack') # a2= Author(name='raun') # a3= Author(name='tran') # # # # b1.authors=[a1,a3] # b2.authors=[a2,a3] # b3.authors=[a1,a2,a3] # # # session.add_all([b1,b2,b3,a1,a2,a3]) session.add_all([b3]) #查询jack 的书 author_obj = session.query(Author).filter(Author.name=='jack').first() print("------------------------") print(author_obj.books) #java 书的作者 book_obj = session.query(Book).filter(Book.name=='java').first() print("------------------------") print(book_obj.authors) session.commit()