今天来聊一聊 Python 的 ORM 框架 SQLAlchemy
SQLAlchemy 没有 Django 的 Models 好用！因为models是Django自带的ORM框架,也正是因为是Django原生的,所以兼容性远远不如SQLAlchemy
真正算得上全面的ORM框架必然是我们的SQLAlchemy ORM框架,它可以在多语言中使用SQL查询
SQLAlchemy 如何使用:
一.下载
pip isntall SQLALchemy
二.创建数据表
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base() # Base是 ORM模型的基类
# ORM模型：
# obj里面的属性 == table中创建的字段
# obj定义table的操作方式和属性
from sqlalchemy import Column, Integer, INT, INTEGER, VARCHAR, String
# 1.创建一个class
class User(Base):
__tablename__ = 'user'
id = Column(Integer, primary_key=True, autoincrement=True)
name = Column(String(32), index=True)
# 2.创建数据引擎
from sqlalchemy import create_engine
engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/sqlalchemy_test?charset=utf8")
# 3.将所有继承Base的class序列化成数据表
Base.metadata.create_all(engine)
三 . 增删改查操作
1.增加数据
# 可视化工具中，分四步操作数据 # 1.选中数据库 - 创建数据库引擎 导入数据库引擎 # 2.创建查询窗口,必须是选中数据库的查询窗口 # 3.创建sql语句 # 4.点击运行 # 1.选中数据库 - 创建数据库引擎 导入数据库引擎 from create_table import engine # 2.创建查询窗口,必须是选中数据库的查询窗口 from sqlalchemy.orm import sessionmaker Session_window = sessionmaker(engine) # 打开查询窗口 db_session = Session_window() # 1.增加数据 原生sql # insert into table(字段) value('123') # from create_table import User # 获取User类 # # user_obj = User(name='小明') # 相当于创建sql语句 # db_session.add(user_obj) # 将sql语句粘贴到查询窗口中 # db_session.commit() # 执行全部语句 # db_session.close() # 关闭连接 # # 2.增加多条数据 from create_table import User user_obj_list = [User(name='赵丽颖'), User(name='江疏影')] db_session.add_all(user_obj_list) # 添加所有的语句 db_session.commit() db_session.close()
2.查询数据
# 原生sql语句 # select * from table # 创建查询窗口 from create_table import engine, User from sqlalchemy.orm import sessionmaker Session = sessionmaker(engine) # 创建数据引擎 db_session = Session() # 打开查询窗口 # # 1.查询数据 user_obj = db_session.query(User).first() print(user_obj.id, user_obj.name) # 1 小明 # 第一个数据 user_obj_list = db_session.query(User).all() for user in user_obj_list: print(user.id, user.name) # 所有的数据 # 2.带条件的查询 # 2.1 根据表达式获取数据 user_obj_list = db_session.query(User).filter(User.id <= 2, User.name == '赵丽颖').all() print(user_obj_list) for user in user_obj_list: print(user.id, user.name) # 根据id条件和name的名字获取到数据 # 根据指定条件获取数据 user_obj_list = db_session.query(User).filter_by(id=2, name="赵丽颖").all() print(user_obj_list) for user in user_obj_list: print(user.id, user.name)
3.修改更新数据
# 原生sql: update table set name = '123' # 创建查询窗口 from create_table import engine, User from sqlalchemy.orm import sessionmaker Session = sessionmaker(engine) # 创建数据引擎 db_session = Session() # 打开查询窗口 # 1. 修改一条数据 user_obj = db_session.query(User).filter(User.id == 1).update({'name': '小明1'}) print(user_obj) # 打印的是库中受影响的数量 db_session.commit() # 修改多条数据 user_obj = db_session.query(User).filter(User.id >= 1).update({'name': '111'}) db_session.commit() # name 全部修改为 111
4.删除数据
# sql原生： delete from table # 创建查询窗口 from create_table import engine, User from sqlalchemy.orm import sessionmaker Session = sessionmaker(engine) # 创建数据引擎 db_session = Session() # 打开查询窗口 # 1.删除单条数据 res = db_session.query(User).filter(User.id == 1).delete() db_session.commit() # 2.删除多条数据 res = db_session.query(User).filter(User.id>=1).delete() db_session.commit()
四 . 一对多的操作
1.创建数据表及关系relationship
from sqlalchemy.ext.declarative import declarative_base # 导入 sqlalchemy 基类 from sqlalchemy import Column, INT, VARCHAR, ForeignKey # 导入字段和类型 from sqlalchemy.orm import relationship # 从orm中导入relationship的关系映射 Base = declarative_base() # 实例化一个基类 class School(Base): __tablename__ = 'school' id = Column(INT, primary_key=True) name = Column(VARCHAR(32)) class Student(Base): __tablename__ = 'student' id = Column(INT, primary_key=True) # int + 主键 默认自增长 name = Column(VARCHAR(32)) # 这里的ForeignKey一定要是 表名.id 不是对象名 school_id = Column(INT, ForeignKey('school.id')) # 对应学校的外键 # 将student和school 创建关系，这个不是字段 ，只是关系， backref是反向关联的关键字 stu2sch = relationship('School', backref='sch2stu') # 创建引擎 from sqlalchemy import create_engine engine = create_engine('mysql+pymysql://root:123@127.0.0.1:3306/sqlalchemy_test?charset=utf8') Base.metadata.create_all(engine) # 创建表
2.基于relationship增加数据
from sqlalchemy.orm import sessionmaker from foreingKey一对多.create_table_ForeignKey import engine, School, Student # 创建操作窗口 Session = sessionmaker(engine) db_session = Session() # 1.增加数据 # # 添加学校表数据 # sch_obj = School(name='beijingSchool') # db_session.add(sch_obj) # db_session.commit() # # # # 笨办法 # # 获取学校对象 # sch_obj = db_session.query(School).filter(School.name == 'beijingSchool').first() # # 将要写入的学生对象 # stu_obj = Student(name='小明', school_id=sch_obj.id) # 写入关联的学校 # db_session.add(stu_obj) # db_session.commit() # # 2 Relationship 版 添加数据操作 - 正向 # stu_obj = Student(name='小红', stu2sch=School(name='beijingSchool')) # db_session.add(stu_obj) # db_session.commit() # 3 Relationship 版 添加数据操作 - 反向 sch_obj = School(name="beijingSchool") sch_obj.sch2stu = [Student(name="赵丽颖"),Student(name="陈妍希")] db_session.add(sch_obj) db_session.commit()
3.基于relationship查询数据
from sqlalchemy.orm import sessionmaker from foreingKey一对多.create_table_ForeignKey import engine, School, Student Session = sessionmaker(engine) db_session = Session() # # 1.查询 笨 # sch_obj = db_session.query(School).filter(School.name == 'beijingSchool').first() # beijing_stu_obj = db_session.query(Student).filter(Student.school_id == sch_obj.id).first() # print(beijing_stu_obj.id, beijing_stu_obj.name) # # 2.relationship 正向查询 # stu_obj = db_session.query(Student).filter(Student.name=='小明').first() # print(stu_obj.name, stu_obj.stu2sch.name) # # 3.relationship 反向查询 # sch_obj_list = db_session.query(School).all() # for sch_obj in sch_obj_list: # for stu in sch_obj.sch2stu: # print(sch_obj.name, stu.name)
五 . 多对多的操作
1.创建表关系
from sqlalchemy.ext.declarative import declarative_base Base = declarative_base() # d导入并创建基类 # 导入字段和属性 导入orm 的关系映射 from sqlalchemy import Column, Integer, String, ForeignKey from sqlalchemy.orm import relationship class Girls(Base): __tablename__ = 'girl' id = Column(Integer, primary_key=True) name = Column(String(32)) g2b = relationship('Boys', backref='b2g', secondary='hotel') # 建立GirlS 和Boys的关系映射 class Boys(Base): __tablename__ = 'boy' id = Column(Integer, primary_key=True) name = Column(String(32)) class Hotel(Base): __tablename__ = 'hotel' id = Column(Integer, primary_key=True) boy_id = Column(Integer, ForeignKey("boy.id")) # boy 的外键 girl_id = Column(Integer, ForeignKey("girl.id")) # girl 的外键 # 创建引擎 from sqlalchemy import create_engine engine = create_engine('mysql+pymysql://root:123@127.0.0.1:3306/sqlalchemy_test?charset=utf8') Base.metadata.create_all(engine) # 创建表
2.基于relationship增加数据
from 多对多.create_table_m2m import engine, Boys, Girls, Hotel from sqlalchemy.orm import sessionmaker Session = sessionmaker(engine) db_session = Session() # 1.增加数据 - relationship 正向 # # girl_obj = Girls(name="赵丽颖") # girl_obj.g2b = [Boys(name="小明")] # db_session.add(girl_obj) # db_session.commit() # 2.增加数据 - relationship 反向 boy_obj = Boys(name="小刚") boy_obj.b2g = [Girls(name="111"),Girls(name="222")] db_session.add(boy_obj) db_session.commit()
3.基于relationship查询数据
from 多对多.create_table_m2m import engine, Boys, Girls, Hotel from sqlalchemy.orm import sessionmaker Session = sessionmaker(engine) db_session = Session() # 1.查询数据 - relationship 正向 girl_obj_list = db_session.query(Girls).all() for girl in girl_obj_list: for boy in girl.g2b: print(girl.name,boy.name) # 2.查询数据 - relationship 反向 boy_obj_list = db_session.query(Boys).all() for boy in boy_obj_list: for girl in boy.b2g: print(girl.name, boy.name)