ORM的主要实现方式

1. SqlObject
2. peewee
3. Django's ORM
4. SQLAlchemy

SQLAlchemy原理图

SQLAlchemy原理图.png

安装SQLAlchemy

#安装
pip install SQLAlchemy

#测试
>>> import sqlalchemy
>>> sqlalchemy.__version__
1.1.9

常见类型

Integer
Float
Boolean
ForeignKey
Date/DateTime
String

更多数据类型>>

连接数据库

from sqlalchemy import Column, Integer, String, DateTime, Boolean

engine = create_engine("mysql://root:@127.0.0.1:3306/news?charset=utf8")

其它数据库的连接方式>>

Declare a Mapping

from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker
from sqlalchemy import Column, Integer, String, DateTime, Boolean

engine = create_engine("mysql://root:@127.0.0.1:3308/news?charset=utf8")

Session = sessionmaker(bind=engine)

Base = declarative_base()

class News(Base):
    ''' 新闻类型 '''
    __tablename__ = 'news'
    id = Column(Integer, primary_key=True)
    title = Column(String(200), nullable=False)
    content = Column(String(2000), nullable=False)
    types = Column(String(10), nullable=False)
    image = Column(String(300))
    author = Column(String(20))
    view_count = Column(Integer)
    created_at = Column(DateTime)
    is_valid = Column(Boolean)

    def __repr__(self):
        return '<News %r>' % self.title

创建数据库

#在终端输入以下命令
>>> from test_mysql_orm import engine
>>> News.metadata.create_all(engine)

增加session

#The ORM’s “handle” to the database is the [`Session`]

from sqlalchemy.orm import sessionmaker

Session = sessionmaker(bind=engine) #绑定engine

新增数据

    def add_one(self):
        ''' 添加数据 '''
        #实例化对象
        new_obj = News(
            title='ORM标题',
            content='content',
            types="百家"
        )
        self.session.add(new_obj)
        self.session.commit()
        return new_obj

查询数据

    def get_one(self):
        ''' 获取一条数据 '''
        return self.session.query(News).get(1)

    def get_more(self):
        ''' 获取多条数据 '''
        return self.session.query(News).filter_by(is_valid=1)

更多查询语法请查看文档>>>

修改数据

    def update_data(self):
        ''' 修改数据 '''
        obj = self.session.query(News).get(38)
        obj.is_valid = 0
        self.session.add(obj)
        self.session.commit()
        return obj

删除数据

    def delete_data(self):
        ''' 删除数据 '''
        # 获取要删除的数据
        data = self.session.query(News).get(39)
        self.session.delete(data)
        self.session.commit()

汇总操作数据库

class MysqlOrmTest(object):

    def __init__(self):
        self.session = Session()

    def add_one(self):
        ''' 添加数据 '''
        new_obj = News(
            title='ORM标题',
            content='content',
            types="百家"
        )
        self.session.add(new_obj)
        self.session.commit()
        return new_obj

    def get_one(self):
        ''' 获取一条数据 '''
        return self.session.query(News).get(1)

    def get_more(self):
        ''' 获取多条数据 '''
        return self.session.query(News).filter_by(is_valid=1)

    def update_data(self):
        ''' 修改数据 '''
        obj = self.session.query(News).get(38)
        obj.is_valid = 0
        self.session.add(obj)
        self.session.commit()
        return obj

    def delete_data(self):
        ''' 删除数据 '''
        # 获取要删除的数据
        data = self.session.query(News).get(39)
        self.session.delete(data)
        self.session.commit()

def main():
    obj = MysqlOrmTest()
    # rest = obj.add_one()
    # print(dir(rest))
    # print(obj.get_one().title)

    # print(obj.get_more().count())
    # for row in obj.get_more():
    #     print(row.title)

    # print(obj.update_data())

    obj.delete_data()

if __name__ == '__main__':
    main()