python学习之路-13

SQLAlchemy ORM框架

连表操作

• 一对多

  • 创建表 指定约束 ForeignKey

  
  from sqlalchemy import create_engine
  from sqlalchemy.ext.declarative import declarative_base
  from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index
  from sqlalchemy.orm import sessionmaker, relationship
  
  engine = create_engine("mysql+pymysql://tuocigaoshou:Eb^BEF38E9FBC36CA775@111.204.117.99:3306/test", max_overflow=5)
  
  Base = declarative_base()
  
  # 一对多
  class Group(Base):
      __tablename__ = "group"
      nid = Column(Integer, primary_key=True, autoincrement=True)
      caption = Column          # 组名
  
  class User(Base):
      __tablename__ = "user"
      nid = Column(Integer, primary_key=True, autoincrement=True)
      username = Column(String(32))
      group_id = Column(Integer, ForeignKey("group.nid"))  # 外键
  
  Base.metadata.create_all(engine)
  

  • 插入数据

  from sqlalchemy import create_engine
  from sqlalchemy.ext.declarative import declarative_base
  from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index
  from sqlalchemy.orm import sessionmaker, relationship
  
  engine = create_engine("mysql+pymysql://tuocigaoshou:Eb^BEF38E9FBC36CA775@111.204.117.99:3306/test", max_overflow=5)
  
  Base = declarative_base()
  
  # 单表
  class Test(Base):
      __tablename__ = "test"
      nid = Column(Integer, primary_key=True, autoincrement=True)
      name = Column(String(32))
  
  # 一对多
  class Group(Base):
      __tablename__ = "group"
      nid = Column(Integer, primary_key=True, autoincrement=True)
      caption = Column(String(32))          # 组名
  
  class User(Base):
      __tablename__ = "user"
      nid = Column(Integer, primary_key=True, autoincrement=True)
      username = Column(String(32))
      group_id = Column(Integer, ForeignKey("group.nid"))  # 外键
  
  # Base.metadata.create_all(engine)    # 创建表
  # Base.metadata.drop_all(engine)    # 删除表
  
  Session = sessionmaker(bind=engine)
  session = Session()
  
  ### 添加数据
  # 向表中添加单条数据
  session.add(Group("dba"))
  session.add(Group("ddd"))
  
  # 向表中添加多条数据
  session.add_all(
      [
          User(username="a", group_id=1),
          User(username="b", group_id=2),
          User(username="c", group_id=1)
      ]
  )
  
  session.commit()
  

  • 查询数据

  
  from sqlalchemy import create_engine
  from sqlalchemy.ext.declarative import declarative_base
  from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index
  from sqlalchemy.orm import sessionmaker, relationship
  
  engine = create_engine("mysql+pymysql://tuocigaoshou:Eb^BEF38E9FBC36CA775@111.204.117.99:3306/test", max_overflow=5)
  
  Base = declarative_base()
  
  ### 创建表结构
  # 单表
  class Test(Base):
      __tablename__ = "test"
      nid = Column(Integer, primary_key=True, autoincrement=True)
      name = Column(String(32))
  
  # 一对多
  class Group(Base):
      __tablename__ = "group"
      nid = Column(Integer, primary_key=True, autoincrement=True)
      caption = Column(String(32))          # 组名
  
  class User(Base):
      __tablename__ = "user"
      nid = Column(Integer, primary_key=True, autoincrement=True)
      username = Column(String(32))
      group_id = Column(Integer, ForeignKey("group.nid"))  # 外键
  
      # 与生成表结构无关，仅用于更方便的进行连表查询
      group = relationship("Group", backref="user")
  
      def __repr__(self):
          temp = "%s - %s - %s" % (self.nid, self.username, self.group_id)
          return temp
  
  # Base.metadata.create_all(engine)    # 创建表
  # Base.metadata.drop_all(engine)    # 删除表
  
  Session = sessionmaker(bind=engine)
  session = Session()
  
  """
  ### 添加数据
  # 向表中添加单条数据
  session.add(Group("dba"))
  session.add(Group("ddd"))
  
  # 向表中添加多条数据
  session.add_all(
      [
          User(username="a", group_id=1),
          User(username="b", group_id=2),
          User(username="c", group_id=1)
      ]
  )
  
  session.commit()
  """
  
  # # 查询单表中所有数据
  # ret = session.query(User).all()
  # print(ret)  # 输出User类中__repr__方法中返回的字符串
  # for obj in ret:
  #     print(obj.nid, obj.username, obj.group_id)
  #
  # # 通过指定列查询
  # ret = session.query(User.nid, User.username).all()
  # print(ret)  # 返回一个列表,列表中包含每一行的数据  [(2, 'a'), (3, 'b'), (4, 'c')]
  
  # # 根据指定条件查询
  # ret = session.query(User).filter(User.username == "a").all()
  # obj = ret[0]
  # print(obj.nid, obj.username, obj.group_id)
  
  # 连表查询
  
  # 通过join进行连表查询
  # ret = session.query(User).join(Group)   # 返回执行的sql语句
  # print(ret)
  # print("------")
  # ret = session.query(User).join(Group).all()
  # for obj in ret:
  #     print(obj.nid, obj.username, obj.group_id)
  #
  # ret = session.query(User, Group).join(Group).all()
  # print(ret)
  #
  #
  # ret = session.query(User.username, Group.caption).join(Group).all()
  # print(ret)
  
  # 通过relationship在创建表的类中指定连表的对应关系,然后进行连表查询
  # 正向查询  (正向查找不能够过滤组的字段)
  ret = session.query(User).all()
  for obj in ret:
      # obj代指user表中的每一行数据
      # obj.group代指obj当前对应的group表中数据的对象
      print(obj.nid, obj.username, obj.group_id, obj.group, obj.group.nid, obj.group.caption)
  
  # 反向查询
  # 查找所有组名为dba的用户信息
  obj = session.query(Group).filter(Group.caption=="dba").first()
  print(obj.nid, obj.caption, obj.user)    # obj.user 这个地方的user是在User类中使用relationship创建对应关系中 backref对应的值
  

• 多对多

  • 原始方法和新式方法1

  ### 关系在第三张表中
  
  from sqlalchemy import create_engine
  from sqlalchemy.ext.declarative import declarative_base
  from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index
  from sqlalchemy.orm import sessionmaker, relationship
  
  engine = create_engine("mysql+pymysql://tuocigaoshou:Eb^BEF38E9FBC36CA775@111.204.117.99:3306/test", max_overflow=5)
  
  Base = declarative_base()
  
  class Host(Base):
      """
      主机表
      """
      __tablename__ = "host"
      nid = Column(Integer, primary_key=True, autoincrement=True)
      hostname = Column(String(32))
      port = Column(String(32))
      ip = Column(String(32))
  
  class HostUser(Base):
      """
      登录主机的用户表
      """
      __tablename__ = "host_user"
      nid = Column(Integer, primary_key=True, autoincrement=True)
      username = Column(String(32))
  
  class Host_HostUser(Base):
      """
      关系表
      """
      __tablename__ = "host_to_host_user"
      nid = Column(Integer, primary_key=True, autoincrement=True)
      host_id = Column(Integer, ForeignKey("host.nid"))
      host_user_id = Column(Integer, ForeignKey("host_user.nid"))
  
      host = relationship("Host", backref="h")
      host_user = relationship("HostUser", backref="u")
  
  # Base.metadata.create_all(engine)    # 创建表
  
  Session = sessionmaker(bind=engine)
  session = Session()
  
  # # 向host主机表中添加多条数据
  # session.add_all(
  #     [
  #         Host(hostname="c1", port="22", ip="1.1.1.1"),
  #         Host(hostname="c2", port="22", ip="1.1.1.2"),
  #         Host(hostname="c3", port="22", ip="1.1.1.3"),
  #     ]
  # )
  
  # # 向host_user登录主机用户表中添加多条数据
  # session.add_all(
  #     [
  #         HostUser(username="root"),
  #         HostUser(username="aa"),
  #         HostUser(username="bb"),
  #         HostUser(username="cc"),
  #     ]
  # )
  
  # # 向host_to_host_user关系表中添加多条数据
  # session.add_all(
  #     [
  #         Host_HostUser(host_id=1, host_user_id=1),
  #         Host_HostUser(host_id=1, host_user_id=2),
  #         Host_HostUser(host_id=1, host_user_id=3),
  #         Host_HostUser(host_id=1, host_user_id=4),
  #         Host_HostUser(host_id=2, host_user_id=2),
  #         Host_HostUser(host_id=2, host_user_id=4),
  #         Host_HostUser(host_id=3, host_user_id=1),
  #         Host_HostUser(host_id=3, host_user_id=3),
  #     ]
  # )
  
  # session.commit()
  
  # 需求:找出能够登录主机名为c1的所有用户
  # ### 原始方式
  # # 从host表中将找到主机名为c1的nid
  # host_obj = session.query(Host).filter(Host.hostname == "c1").first()
  #
  # # 通过主机名为c1的nid在关系表中找到用户的id
  # host_2_host_user = session.query(Host_HostUser.host_user_id).filter(Host_HostUser.host_id==host_obj.nid).all()
  #
  # r = zip(*host_2_host_user)
  # users = session.query(HostUser.username).filter(HostUser.nid.in_(list(r)[0])).all()
  # print(users)
  
  ### 原始方式结合
  ret = session.query(HostUser.username).filter(HostUser.nid.in_(session.query(Host_HostUser.host_user_id).filter(Host_HostUser.host_id == session.query(Host.nid).filter(Host.hostname == 'c1')))).all()
  print(ret)
  
  ### 新式方法
  # 通过在Host_HostUser类中使用relationship建立与Host类和HostUser类建立关系,然后使用反向查询和正向询进行查找
  host_obj = session.query(Host).filter(Host.hostname=="c1").first()
  for item in host_obj.h:   # host_obj.h 反向查询
      print(item.host_user.username)  # item.host_user.username  正向查询
  

  • 新式方法2

  ### 关系在第1张表中 secondary=Host_HostUser.__table__ 要将关系表放在最上面 如果不使用lambda则应该将关系表放在最上面
  
  from sqlalchemy import create_engine
  from sqlalchemy.ext.declarative import declarative_base
  from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index
  from sqlalchemy.orm import sessionmaker, relationship
  
  engine = create_engine("mysql+pymysql://tuocigaoshou:Eb^BEF38E9FBC36CA775@111.204.117.99:3306/test", max_overflow=5)
  
  Base = declarative_base()
  
  class Host_HostUser(Base):
      """
      关系表
      """
      __tablename__ = "host_to_host_user"
      nid = Column(Integer, primary_key=True, autoincrement=True)
      host_id = Column(Integer, ForeignKey("host.nid"))
      host_user_id = Column(Integer, ForeignKey("host_user.nid"))
  
  class Host(Base):
      """
      主机表
      """
      __tablename__ = "host"
      nid = Column(Integer, primary_key=True, autoincrement=True)
      hostname = Column(String(32))
      port = Column(String(32))
      ip = Column(String(32))
  
      host_user = relationship("HostUser",
                               secondary=Host_HostUser.__table__,
                               backref="h")
  
  class HostUser(Base):
      """
      登录主机的用户表
      """
      __tablename__ = "host_user"
      nid = Column(Integer, primary_key=True, autoincrement=True)
      username = Column(String(32))
  
  # Base.metadata.create_all(engine)    # 创建表
  
  Session = sessionmaker(bind=engine)
  session = Session()
  
  # # 向host主机表中添加多条数据
  # session.add_all(
  #     [
  #         Host(hostname="c1", port="22", ip="1.1.1.1"),
  #         Host(hostname="c2", port="22", ip="1.1.1.2"),
  #         Host(hostname="c3", port="22", ip="1.1.1.3"),
  #     ]
  # )
  
  # # 向host_user登录主机用户表中添加多条数据
  # session.add_all(
  #     [
  #         HostUser(username="root"),
  #         HostUser(username="aa"),
  #         HostUser(username="bb"),
  #         HostUser(username="cc"),
  #     ]
  # )
  
  # # 向host_to_host_user关系表中添加多条数据
  # session.add_all(
  #     [
  #         Host_HostUser(host_id=1, host_user_id=1),
  #         Host_HostUser(host_id=1, host_user_id=2),
  #         Host_HostUser(host_id=1, host_user_id=3),
  #         Host_HostUser(host_id=1, host_user_id=4),
  #         Host_HostUser(host_id=2, host_user_id=2),
  #         Host_HostUser(host_id=2, host_user_id=4),
  #         Host_HostUser(host_id=3, host_user_id=1),
  #         Host_HostUser(host_id=3, host_user_id=3),
  #     ]
  # )
  
  # session.commit()
  
  # 需求:找出能够登录主机名为c1的所有用户
  ### 新式方法二
  
  host_obj = session.query(Host).filter(Host.hostname=="c1").first()
  print(host_obj.host_user)
  

  • 新式方法三

  ### secondary="host_to_host_user" 关系表无顺序要求 如果不使用lambda则应该将关系表放在最上面
  
  from sqlalchemy import create_engine
  from sqlalchemy.ext.declarative import declarative_base
  from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index
  from sqlalchemy.orm import sessionmaker, relationship
  
  engine = create_engine("mysql+pymysql://tuocigaoshou:Eb^BEF38E9FBC36CA775@111.204.117.99:3306/test", max_overflow=5)
  
  Base = declarative_base()
  
  class Host(Base):
      """
      主机表
      """
      __tablename__ = "host"
      nid = Column(Integer, primary_key=True, autoincrement=True)
      hostname = Column(String(32))
      port = Column(String(32))
      ip = Column(String(32))
  
      host_user = relationship("HostUser",
                               secondary="host_to_host_user",
                               backref="h")
  
  class HostUser(Base):
      """
      登录主机的用户表
      """
      __tablename__ = "host_user"
      nid = Column(Integer, primary_key=True, autoincrement=True)
      username = Column(String(32))
  
  class Host_HostUser(Base):
      """
      关系表
      """
      __tablename__ = "host_to_host_user"
      nid = Column(Integer, primary_key=True, autoincrement=True)
      host_id = Column(Integer, ForeignKey("host.nid"))
      host_user_id = Column(Integer, ForeignKey("host_user.nid"))
  
  # Base.metadata.create_all(engine)    # 创建表
  
  Session = sessionmaker(bind=engine)
  session = Session()
  
  ### 新式方法三
  
  host_obj = session.query(Host).filter(Host.hostname=="c1").first()
  print(host_obj.host_user)
  

  • 新式方法四

  ### secondary=lambda : Host_HostUser.__table__  如果不使用lambda则应该将关系表放在最上面
  
  from sqlalchemy import create_engine
  from sqlalchemy.ext.declarative import declarative_base
  from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index
  from sqlalchemy.orm import sessionmaker, relationship
  
  engine = create_engine("mysql+pymysql://tuocigaoshou:Eb^BEF38E9FBC36CA775@111.204.117.99:3306/test", max_overflow=5)
  
  Base = declarative_base()
  
  class Host(Base):
      """
      主机表
      """
      __tablename__ = "host"
      nid = Column(Integer, primary_key=True, autoincrement=True)
      hostname = Column(String(32))
      port = Column(String(32))
      ip = Column(String(32))
  
      host_user = relationship("HostUser",
                               secondary=lambda : Host_HostUser.__table__,
                               backref="h")
  
  class HostUser(Base):
      """
      登录主机的用户表
      """
      __tablename__ = "host_user"
      nid = Column(Integer, primary_key=True, autoincrement=True)
      username = Column(String(32))
  
  class Host_HostUser(Base):
      """
      关系表
      """
      __tablename__ = "host_to_host_user"
      nid = Column(Integer, primary_key=True, autoincrement=True)
      host_id = Column(Integer, ForeignKey("host.nid"))
      host_user_id = Column(Integer, ForeignKey("host_user.nid"))
  
  # Base.metadata.create_all(engine)    # 创建表
  
  Session = sessionmaker(bind=engine)
  session = Session()
  
  ### 新式方法四
  
  host_obj = session.query(Host).filter(Host.hostname=="c1").first()
  print(host_obj.host_user)
  

  • 新式方法五

  ### 关系表需要使用Table()进行创建
  ### relationship 中secondary=Host_HostUser, 如果不使用lambda则应该将关系表放在最上面
  
  from sqlalchemy import create_engine
  from sqlalchemy.ext.declarative import declarative_base
  from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index, Table
  from sqlalchemy.orm import sessionmaker, relationship
  
  engine = create_engine("mysql+pymysql://tuocigaoshou:Eb^BEF38E9FBC36CA775@111.204.117.99:3306/test", max_overflow=5)
  
  Base = declarative_base()
  
  Host_HostUser = Table('host_to_host_user', Base.metadata,
                Column('nid', Integer, primary_key=True, autoincrement=True),
                Column('host_id', Integer, ForeignKey("host.nid")),
                Column('host_user_id', Integer, ForeignKey("host_user.nid")),
  )
  
  class Host(Base):
      """
      主机表
      """
      __tablename__ = "host"
      nid = Column(Integer, primary_key=True, autoincrement=True)
      hostname = Column(String(32))
      port = Column(String(32))
      ip = Column(String(32))
  
      host_user = relationship("HostUser",
                               secondary=Host_HostUser,
                               backref="h")
  
  class HostUser(Base):
      """
      登录主机的用户表
      """
      __tablename__ = "host_user"
      nid = Column(Integer, primary_key=True, autoincrement=True)
      username = Column(String(32))
  
  # Base.metadata.create_all(engine)    # 创建表
  
  Session = sessionmaker(bind=engine)
  session = Session()
  
  ### 新式方法五
  
  host_obj = session.query(Host).filter(Host.hostname=="c1").first()
  print(host_obj.host_user)
  

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