python3 sqlalchemy orm数据库使用

orm 是面向对象数据库，可有效避免写sql语句繁琐，最近了解一下感觉很不错，后面 贴代码，连接数据库我是使用 mysqlconnector库，在你的pycharm里面安装这个包，然后 打开数据 ：net start mysql，用命令行创建数据库，创建表就可以orm了（ tablename = ‘users’），创建了 users表，MySqlManager 是来测试数据库操作的，习惯使用面向对象来做一些demo，代卖注释很详细

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

# https://www.cnblogs.com/ray-mmss/p/9424978.html
Base = declarative_base()

class MySqlManager(object):

    def __init__(self):
        self.engine = create_engine('mysql+mysqlconnector://root:123@localhost/test',
                           max_overflow=0,  # 超过连接池大小外最多创建的连接
                           pool_size=5,  # 连接池大小
                           pool_timeout=30,  # 池中没有线程最多等待的时间，否则报错
                           pool_recycle=-1  # 多久之后对线程池中的线程进行一次连接的回收（重置）
                           )
        self.create_all()
        # 根据引擎创建session工厂
        self.SessionFactory = sessionmaker(bind=self.engine)
        # 用session工厂创建一个session对象
        self.session = self.SessionFactory()
        # 根据Users类对users表进行增删改查

# 添加数据
    def add_datas(self):
        obj1 = Student(username='bob0',password='123',email='[email protected]')
        obj2 = Student(username='bob1', password='135', email='[email protected]')
        # self.session.add(obj1)
        self.session.add_all([obj1,obj2])
        self.session.commit()
# 删除数据库
    def delete_datas(self):
        self.session.query(Student).filter(Student.username == 'bob123').delete()
        self.session.commit()
#修改数据库
    def update_datas(self):
        self.session.query(Student).filter(Student.id == 6).\
            update({Student.username :'bob123'})
        self.session.query(Student).filter(Student.id == 7).\
            update({Student.username : 'bob456'})
        self.session.query(Student).filter(Student.id==9).\
            update({Student.username:Student.username+"HUB"},synchronize_session=False)
        self.session.commit()

    #查询数据
    def search_datas(self):
        result = self.session.query(Student).all()
        for row in result:
            print(row.id,row.username,row.password,row.email)

        # result = self.session.query(Student).filter(Student.id >= 1)
        # for row in result:
        #     print(row.id, row.username, row.password, row.email)
        #
        # result = self.session.query(Student).filter(Student.id >= 1).first
        # print(result)
    # 关闭数据库
    def closeSession(self):
        # 关闭session
        self.session.close()

    def create_all(self):
        Base.metadata.create_all(self.engine)

    def drop_all(self):
        Base.metadata.drop_all(self.engine)





class Student(Base):
    __tablename__ = 'users'
    id = Column(Integer,primary_key=True)
    username = Column(String(64),nullable=False,index=True)
    password = Column(String(64),nullable=False)
    email = Column(String(64),nullable=False,index=True)

    def __repr__(self):
        return '%s(%r)'%(self.__class__.__name__,self.username)

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