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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python学习之路-13

SQLAlchemy ORM框架

连表操作

paramiko模块

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