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标签:sch   sql   lse   end   str   iso   def   文件的   sel   

今日所学内容:

    一、SQLAlchemy

    二、创建表

    三、操作表

一、SQLAlchemy?

  1、什么是SQLAlchemy
    SQLAlchemy是Python编程语言下的一款ORM框架,该框架建立在数据库API之上,使用关系对象映射进行数据库操作,简言之便是:将对象转换成SQL,然后使用数据API执行SQL并获取执行结果。
  2、安装SQLAlchemy
    pip install SQLAlchemy 或者 在Python的setting中添加
  3、怎么使用SQLAlchemy
    SQLAlchemy本身无法操作数据库,其必须以来pymsql等第三方插件,Dialect用于和数据API进行交流,根据配置文件的不同调用不同的数据库API,从而实现对数据库的操作
  4、ORM功能的使用:
    使用 ORM/Schema Type/SQL Expression Language/Engine/ConnectionPooling/Dialect 所有组件对数据进行操作。根据类创建对象,对象转换成SQL,执行SQL。

二、创建表

  导入模块

    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

  创建引擎

    engine = create_engine("mysql+pymysql://root:000000@127.0.0.1:3306/t1?charset=utf8", max_overflow=5)

  实例化Base类

    Base = declarative_base()

  创建单表

    class Users(Base):
      __tablename__ = ‘users‘
      id = Column(Integer, primary_key=True)
      name = Column(VARCHAR(32))
      extra = Column(VARCHAR(16))

    __table_args__ = (
      UniqueConstraint(‘id‘, ‘name‘, name=‘uix_id_name‘),
      Index(‘ix_id_name‘, ‘name‘, ‘extra‘),
     )

    一对多

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

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

    多对多
      class Group(Base):
        __tablename__ = ‘group‘
        id = Column(Integer, primary_key=True)
        name = Column(VARCHAR(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(VARCHAR(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.id‘))

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

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

     # create_db();
     # drop_db();

三、操作表

  导入模块

    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

  创建引擎

    engine = create_engine("mysql+pymysql://root:000000@127.0.0.1:3306/t1?charset=utf8", max_overflow=5)

  实例化Base类

    Base = declarative_base()

  创建单表

    class Users(Base):
      __tablename__ = ‘users‘
      id = Column(Integer, primary_key=True)
      name = Column(VARCHAR(32))
      extra = Column(VARCHAR(16))

    __table_args__ = (
      UniqueConstraint(‘id‘, ‘name‘, name=‘uix_id_name‘),
      Index(‘ix_id_name‘, ‘name‘, ‘extra‘),
     )

    def __repr__(self):
      return "%s-%s" %(self.id, self.name)

    一对多

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

      def __repr__(self):
        return "%s-%s" %(self.nid, self.caption)

      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"))

      与生成表结构无关,仅用于查询方便
        favor = relationship("Favor", backref=‘pers‘)

    多对多

      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.id‘))
        group = relationship("Group", backref=‘s2g‘)
        server = relationship("Server", backref=‘s2g‘)

      class Group(Base):
        __tablename__ = ‘group‘
        id = Column(Integer, primary_key=True)
        name = Column(String(64), unique=True, nullable=False)
        port = Column(Integer, default=22)
        # group = relationship(‘Group‘,secondary=ServerToGroup,backref=‘host_list‘)

      class Server(Base):
        __tablename__ = ‘server‘
        id = Column(Integer, primary_key=True, autoincrement=True)
        hostname = Column(String(64), unique=True, nullable=False)

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

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

     # create_db();
     # drop_db();

    Session = sessionmaker(bind=engine)
    session = Session()

  增加

    增加一条数据

      obj = Users(name="alex0", extra=‘sb‘)
      session.add(obj)

    增加多条数据

      session.add_all([
        Users(name="alex1", extra=‘sb‘),
        Users(name="alex2", extra=‘sb‘),
       ])
      session.commit()

  删除

    session.query(Users).filter(Users.id > 2).delete()
    session.commit()

  修改

    session.query(Users).filter(Users.id > 2).update({"name" : "099"})
    session.commit()

  查询

    ret = session.query(Users).all()
    ret = session.query(Users.name, Users.extra).all()
    ret = session.query(Users).filter_by(name=‘alex‘).all()
    ret = session.query(Users).filter_by(name=‘alex‘).first()

  其它

    条件

      ret = session.query(Users).filter_by(name=‘alex‘).all()
      ret = session.query(Users).filter(Users.id > 1, Users.name == ‘eric‘).all()
      ret = session.query(Users).filter(Users.id.between(1, 3), Users.name == ‘eric‘).all()
      ret = session.query(Users).filter(Users.id.in_([1,3,4])).all()
      ret = session.query(Users).filter(~Users.id.in_([1,3,4])).all()
      ret = session.query(Users).filter(Users.id.in_(session.query(Users.id).filter_by(name=‘eric‘))).all()

     from sqlalchemy import and_, or_
      ret = session.query(Users).filter(and_(Users.id > 3, Users.name == ‘eric‘)).all()
      ret = session.query(Users).filter(or_(Users.id < 2, Users.name == ‘eric‘)).all()
      ret = session.query(Users).filter(
        or_(
        Users.id < 2,
        and_(Users.name == ‘eric‘, Users.id > 3),
        Users.extra != ""
       )).all()

    通配符

      ret = session.query(Users).filter(Users.name.like(‘e%‘)).all()
      ret = session.query(Users).filter(~Users.name.like(‘e%‘)).all()

    限制  limit

      ret = session.query(Users)[1:2]

    排序

      ret = session.query(Users).order_by(Users.name.desc()).all()
      ret = session.query(Users).order_by(Users.name.desc(), Users.id.asc()).all()

    分组

     from sqlalchemy.sql import func
      ret = session.query(Users).group_by(Users.extra).all()
      ret = session.query(
        func.max(Users.id),
        func.min(Users.id)).group_by(Users.name).all()

      ret = session.query(
        func.max(Users.id),
         func.min(Users.id)).group_by(Users.name).having(func.min(Users.id) >2).all()

    连表

      ret = session.query(Users, Favor).filter(Users.id == Favor.nid).all()
      ret = session.query(Person).join(Favor).all()
      ret = session.query(Person).join(Favor, isouter=True).all()

 

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标签:sch   sql   lse   end   str   iso   def   文件的   sel   

原文地址:https://www.cnblogs.com/Chinesehan/p/11047152.html

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