Python中SQLAlchemy模块通过建立orm来对数据库进行操作
1. 建表
方式1
# -*- coding:utf-8 -*- # Author:Wong Du from sqlalchemy import create_engine from sqlalchemy.ext.declarative import declarative_base from sqlalchemy import Column, Integer, String, DATE # 建立镜像连接 engine = create_engine("mysql+pymysql://caiyun:[email protected]/testdb") # 创建orm基类，用于建表结构继承使用 Base = declarative_base() # 创建表Student类 class Student(Base): __tablename__ = 'student' # 表名 id = Column(Integer, nullable=False, primary_key=True, autoincrement=True) name = Column(String(32), nullable=False) register_date = Column(DATE) # 让查询到的数据变得可读 def __repr__(self): return "id:%s name:%s date:%s"\ % (self.id, self.name, self.register_date) # 提交，创建表结构 Base.metadata.create_all(engine)
方式2
1 # -*- coding:utf-8 -*- 2 # Author:Wong Du 3 4 from sqlalchemy import Table, create_engine 5 from sqlalchemy import Column, Integer, String 6 from sqlalchemy.ext.declarative import declarative_base 7 8 # 建立镜像连接 9 engine = create_engine("mysql+pymysql://root:[email protected]/testdb", echo=True) 10 11 # 创建orm基类，用于建表结构继承使用 12 Base = declarative_base() 13 14 # 建表 15 user = Table( 16 'user', Base.metadata, # ‘user’为表名，通过Base的metadata方法建表 17 Column('id', Integer, nullable=False, primary_key=True, autoincrement=True), 18 Column('name', String(32), nullable=False), 19 Column('password', String(64), nullable=False), 20 ) 21 22 # 提交，创建表结构 23 Base.metadata.create_all(engine)
方式3
1 # -*- coding:utf-8 -*- 2 # Author:Wong Du 3 4 from sqlalchemy import Table, MetaData, create_engine 5 from sqlalchemy import Column, Integer, String 6 7 # 创建镜像连接 8 engine = create_engine("mysql+pymysql://root:[email protected]/testdb", echo=True) 9 10 # 创建orm对象 11 metadata = MetaData() 12 13 # 建表 14 user = Table( 15 'user2', metadata, 16 Column('id', Integer, nullable=False, primary_key=True, autoincrement=True), 17 Column('name', String(32), nullable=False), 18 Column('password', String(64), nullable=False), 19 ) 20 21 metadata.create_all(engine)
2. sqlalchemy筛选表内容基本操作
# -*- coding:utf-8 -*- # Author:Wong Du import sqlalchemy_createTable from sqlalchemy.orm import sessionmaker from sqlalchemy import func # 通过绑定镜像连接生成会话类 Session_class = sessionmaker(bind=sqlalchemy_createTable.engine) # 生成会话对象 session = Session_class() # 多条件查询，通过.query方法来查表，.filter方法来筛选表内容 sel_obj = session.query(sqlalchemy_createTable.Student)\ .filter(sqlalchemy_createTable.Student.id>0)\ .filter(sqlalchemy_createTable.Student.id<5).first() # 查询所有数据 sel_obj2 = session.query(sqlalchemy_createTable.Student).all() sel_obj3 = session.query(sqlalchemy_createTable.Student).filter().all() if sel_obj2 == sel_obj3: print("效果相同") # like匹配&统计 sel_obj4 = session.query(sqlalchemy_createTable.Student)\ .filter(sqlalchemy_createTable.Student.name.like("%a%")).count() print(sel_obj4) # 分组统计 sel_obj5 = session.query( sqlalchemy_createTable.Student.name, func.count(sqlalchemy_createTable.Student.name))\ .group_by(sqlalchemy_createTable.Student.name).all() print(sel_obj5)
3. 其他操作
# -*- coding:utf-8 -*- # Author:Wong Du import sqlalchemy_createTable from sqlalchemy.orm import sessionmaker # 创建与engine镜像连接的数据库交互的类 Session_class = sessionmaker(bind=sqlalchemy_createTable.engine) # 生成会话实例 session = Session_class() # 添加/插入表数据，创建要插入的数据对象 ins_stu_obj = sqlalchemy_createTable.Student(name='zhangsan', register_date='2019-12-12') # 将要操作的数据对象添加到会话实例中 session.add(ins_stu_obj) # 提交会话操作对象，使其真正生效 session.commit() # 关闭会话实例 session.close() # 查询表数据 ''' # filter_by关键字表达式，filter数据库SQL表达式，为空则匹配所有 # .first()获取匹配的第一条查询数据，.all()获取匹配的所有数据 # 格式1：session.query(表类名).filter_by(匹配关键字).first() # 格式2：session.query(表类名).filter(匹配SQL语句).all() # 获取查询到的表数据对象，为一个列表形式 sel_stu_obj = session.query(sqlalchemy_createTable.Student).filter_by(name='zhangsan').first() sel_stu_obj2 = session.query(sqlalchemy_createTable.Student).filter(sqlalchemy_createTable.Student.id>0).all() print(sel_stu_obj) print(sel_stu_obj2) print(sel_stu_obj2[1].name) ''' # 修改表数据 ''' # 获取要修改的表数据对象 upd_stu_obj = session.query(sqlalchemy_createTable.Student).filter_by(name='zhangsan').first() print(upd_stu_obj) upd_stu_obj.name = 'ZhangSan' session.commit() sel = session.query(sqlalchemy_createTable.Student).filter_by().first() print(sel) session.close() ''' # 回滚应用例子 upd = session.query(sqlalchemy_createTable.Student).filter(sqlalchemy_createTable.Student.id==7).all() print(upd[0].register_date) upd[0].register_date = '2008-10-01' ins = sqlalchemy_createTable.Student(name='WangWu', register_date='2018-12-12') session.add(ins) print(session.query(sqlalchemy_createTable.Student). filter(sqlalchemy_createTable.Student.register_date. in_(['2008-10-01', '2018-12-12'])).all()) session.rollback() print(session.query(sqlalchemy_createTable.Student). filter(sqlalchemy_createTable.Student.register_date. in_(['2008-10-01', '2018-12-12'])).all())
4. 一对一外键
1 # -*- coding:utf-8 -*- 2 # Author:Wong Du 3 4 from sqlalchemy import create_engine 5 from sqlalchemy.ext.declarative import declarative_base 6 from sqlalchemy import Column, Integer, String, ForeignKey 7 from sqlalchemy.orm import sessionmaker, relationship 8 9 # 创建镜像连接 10 engine = create_engine("mysql+pymysql://caiyun:[email protected]/testdb?charset=utf8") 11 # 创建orm基类 12 Base = declarative_base() 13 14 class User(Base): 15 __tablename__ = 'user' 16 id = Column(Integer, nullable=False, primary_key=True, autoincrement=True) 17 name = Column(String(32), nullable=False) 18 passwd = Column(String(64), nullable=False, default='123456') 19 20 def __repr__(self): 21 return "<id:%d name:%s passwd:%s>" \ 22 % (self.id, self.name, self.passwd) 23 24 class Addr(Base): 25 __tablename__ = 'addr' 26 id = Column(Integer, nullable=False, primary_key=True, autoincrement=True) 27 address = Column(String(32), default='X') 28 u_id = Column(Integer, ForeignKey('user.id'), nullable=False) # 配置外键 29 30 # 通过sqlalchemy内部方法把两张表外键关联起来，从而实现不同表数据的互相调用 31 user = relationship('User', backref='addr') 32 33 def __repr__(self): 34 return "<id:%d address:%s u_id:%d>" \ 35 % (self.id, self.address, self.u_id) 36 37 38 Base.metadata.create_all(engine) 39 40 41 ''' 42 -------------------------------------------------------------------------------------- 43 华丽分隔线 44 -------------------------------------------------------------------------------------- 45 ''' 46 47 Session_class = sessionmaker(bind=engine) 48 session = Session_class() 49 50 # 插入 51 ins_user = User(name='dudu', passwd='dudu814') 52 # ins_user2 = User(name='hongfa', passwd='hongfa814') 53 # ins_user3 = User(name='jinglin', passwd='jinglin814') 54 # 55 # ins_addr = Addr(address='guangzhou', u_id=1) 56 # ins_addr2 = Addr(address='Guangdong', u_id=2) 57 # ins_addr3 = Addr(address='shenzhen', u_id=3) 58 # session.add_all( [ins_user, ins_user2, ins_user3, 59 # ins_addr, ins_addr2, ins_addr3] ) 60 # session.commit() 61 62 sel_user = session.query(User).filter(User.name=='dudu').first() 63 print(sel_user) 64 print(sel_user.addr) 65 print(sel_user.addr[0].address) 66 67 print('\033[33;1m华丽分隔线\033[0m'.center(40, '-')) 68 69 sel_addr = session.query(Addr).all() 70 print(sel_addr) 71 print(sel_addr[2]) 72 print(sel_addr[2].user) 73 print(sel_addr[2].user.passwd)
5. 一对多外键
1 # -*- coding:utf-8 -*- 2 # Author:Wong Du 3 4 from sqlalchemy import create_engine 5 from sqlalchemy.ext.declarative import declarative_base 6 from sqlalchemy import Column, Integer, String, ForeignKey 7 from sqlalchemy.orm import sessionmaker, relationship 8 9 engine = create_engine("mysql+pymysql://caiyun:caiyun814@localhost/testdb?charset=utf8") 10 11 Base = declarative_base() 12 13 14 class Taobao_addr(Base): 15 __tablename__ = 'taobao_addr' 16 id = Column(Integer, nullable=False, primary_key=True, autoincrement=True) 17 addr = Column(String(32), nullable=False, server_default='XXXXXXXXXXXXXXX') 18 19 def __repr__(self): 20 return "<id:%d addr:%s>" \ 21 % (self.id, self.addr) 22 23 class Taobao_user(Base): 24 __tablename__ = 'taobao_user' 25 id = Column(Integer, nullable=False, primary_key=True, autoincrement=True) 26 name = Column(String(32), nullable=False, server_default='X') 27 home_addr_id = Column(Integer, ForeignKey('taobao_addr.id'), nullable=False) 28 work_addr_id = Column(Integer, ForeignKey('taobao_addr.id'), nullable=False) 29 30 # home_addr = relationship('Taobao_addr') 31 # work_addr = relationship('Taobao_addr') 32 home_addr = relationship('Taobao_addr', foreign_keys=home_addr_id) 33 work_addr = relationship('Taobao_addr', foreign_keys=work_addr_id) 34 35 def __repr__(self): 36 return "<id:%d name:%s home_addr_id:%d work_addr_id:%d>" \ 37 %(self.id, self.name, self.home_addr_id, self.work_addr_id) 38 39 Base.metadata.create_all(engine) 40 41 42 ''' 43 -------------------------------------------------------------------------------------- 44 华丽分隔线 45 -------------------------------------------------------------------------------------- 46 ''' 47 48 Session_class = sessionmaker(bind=engine) 49 session = Session_class() 50 51 # 插入数据 52 ''' 53 addr_list = ['ShenZhen', 'GuangZhou', 'BeiJing', 'ShangHai'] 54 ins_addr_list = [] 55 for i in addr_list: 56 obj = Taobao_addr(addr=i) 57 ins_addr_list.append(obj) 58 session.add_all(ins_addr_list) 59 60 ins_user = Taobao_user(name='dudu', home_addr_id=1, work_addr_id=4) 61 ins_user2 = Taobao_user(name='junry', home_addr_id=3, work_addr_id=3) 62 ins_user3 = Taobao_user(name='hongfa', home_addr_id=4, work_addr_id=2) 63 session.add_all([ins_user, ins_user2, ins_user3]) 64 65 session.commit() 66 ''' 67 68 # 查询数据 69 sel_user = session.query(Taobao_user).all() 70 print(sel_user) 71 print(sel_user[0].home_addr) 72 print(sel_user[0].id, sel_user[0].name, 73 sel_user[0].home_addr.addr, 74 sel_user[0].work_addr.addr)