python中orm框架学习

安装sqlalchemy

pip3 install sqlalchemy

创建表结构：

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

import pymysql
#创建对象的基类
Base = declarative_base()
#定义user对象
class User(Base):
    #表的名字
    __tablename__ = 'user'
    #表的结构
    id = Column(Integer,primary_key=True,autoincrement=True)
    name = Column(String(20))
#初始化数据库连接
#数据库类型+数据库驱动名称://用户名:口令@机器地址:端口号/数据库名

engine = create_engine('mysql+pymysql://root:123456@192.168.170.129:3306/learn_orm',max_overflow=5)
Base.metadata.create_all(engine)

#创建DBSession类型
DBSession = sessionmaker(bind=engine)

一对多核多对多

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column,Integer,String,ForeignKey,UniqueConstraint,Index
from sqlalchemy.orm import sessionmaker,relationship
from sqlalchemy import create_engine
engine = create_engine("mysql+pymysql://root:123456@192.168.180.129:3306/test",max_overflow=5)
Base = declarative_base()
#创建单表
class Users(Base):
    __tablename__ = 'users'
    id = Column(Integer,primary_key=True)
    name = Column(String(32))
    extra = Column(String(16))

#一对多

class Favor(Base):
    __tablename__ = 'favor'
    nid = Column(Integer,primary_key=True)
    caption = Column(String(50),default='red',unique=True)

class Person(Base):
    __tablename__ = 'person'
    nid = Column(Integer,primary_key=True)
    name = Column(String(32),index=True,nullable=True)
    favor_id = Column(Integer,ForeignKey('favor.nid'))

#多对多
class Group(Base):
    __tablename__ = 'group'
    nid = Column(Integer,primary_key=True)
    name = Column(String(64),unique=True,nullable=False)
    port = Column(Integer,default=22)

class Server(Base):
    __tablename__ = 'server'
    id = Column(Integer,primary_key=True,autoincrement=True)
    hostname = Column(String(64),unique=True,nullable=False)
class ServerToGroup(Base):
    __tablename__ = 'servertogroup'
    nid = Column(Integer,primary_key=True,autoincrement=True)
    server_id = Column(Integer, ForeignKey('server.id'))
    group_id = Column(Integer, ForeignKey('group.nid'))
# Base.metadata.create_all(engine) #生成表
Base.metadata.drop_all(engine) #生成表

#添加数据(往Users表增加数据)

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column,Integer,String,ForeignKey,UniqueConstraint,Index
from sqlalchemy.orm import sessionmaker,relationship
from sqlalchemy import create_engine
from orm一对多和多对多 import Users  #从orm一对多和对多程序中导入Users类
engine = create_engine("mysql+pymysql://root:123456@192.168.180.129:3306/test",max_overflow=5)
Base = declarative_base()
Base.metadata.create_all(engine) #生成表
# Base.metadata.drop_all(engine) #生成表
Session =  sessionmaker(bind=engine)
session = Session()
#增加数据
obj = Users(name="parktrick",extra="Devops")
session.add(obj)
session.commit()  #不执行这步，数据是写入不了数据库的

#删除User表某条数据

#删除数据
session.query(Users).filter(Users.id > 2).delete() #把Users.id大于2的数据删除掉
session.commit()

#修改数据

#修改数据
session.query(Users).filter(Users.id > 1).update({"name":"bob"}) #修改User.id大于1的name为"bob"
session.commit()