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  • 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。

    SQLAlchemy本身不能对数据库进行操作，得依赖第三方的模块，所以还得安装pymysql

    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，如：

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    MySQL-Python
        mysql+mysqldb://<user>:<password>@<host>[:<port>]/<dbname>
     
    pymysql
        mysql+pymysql://<username>:<password>@<host>/<dbname>[?<options>]
     
    MySQL-Connector
        mysql+mysqlconnector://<user>:<password>@<host>[:<port>]/<dbname>
     
    cx_Oracle
        oracle+cx_oracle://user:pass@host:port/dbname[?key=value&key=value...]
     
    更多详见：http://docs.sqlalchemy.org/en/latest/dialects/index.html

    步骤一：

    使用 Engine/ConnectionPooling/Dialect 进行数据库操作，Engine使用ConnectionPooling连接数据库，然后再通过Dialect执行SQL语句。

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    #!/usr/bin/env python
    # -*- coding:utf-8 -*-
     
    from sqlalchemy import create_engine
     
     
    engine = create_engine("mysql+mysqldb://root:123@127.0.0.1:3306/s11", max_overflow=5)
     
    engine.execute(
        "INSERT INTO ts_test (a, b) VALUES ('2', 'v1')"
    )
     
    engine.execute(
         "INSERT INTO ts_test (a, b) VALUES (%s, %s)",
        ((555, "v1"),(666, "v1"),)
    )
    engine.execute(
        "INSERT INTO ts_test (a, b) VALUES (%(id)s, %(name)s)",
        id=999, name="v1"
    )
     
    result = engine.execute('select * from ts_test')
    result.fetchall()
     事务操作

    注：查看数据库连接：show status like 'Threads%';

    步骤二：

    使用 Schema Type/SQL Expression Language/Engine/ConnectionPooling/Dialect 进行数据库操作。Engine使用Schema Type创建一个特定的结构对象，之后通过SQL Expression Language将该对象转换成SQL语句，然后通过 ConnectionPooling 连接数据库，再然后通过 Dialect 执行SQL，并获取结果。

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    #!/usr/bin/env python
    # -*- coding:utf-8 -*-
     
    from sqlalchemy import create_engine, Table, Column, Integer, String, MetaData, ForeignKey
     
    metadata = MetaData()
     
    user = Table('user', metadata,
        Column('id', Integer, primary_key=True),
        Column('name', String(20)),
    )
     
    color = Table('color', metadata,
        Column('id', Integer, primary_key=True),
        Column('name', String(20)),
    )
    engine = create_engine("mysql+mysqldb://root:123@127.0.0.1:3306/s11", max_overflow=5)
     
    metadata.create_all(engine)
    # metadata.clear()
    # metadata.remove()
     增删改查

    更多内容详见：

        http://www.jianshu.com/p/e6bba189fcbd

        http://docs.sqlalchemy.org/en/latest/core/expression_api.html

    注：SQLAlchemy无法修改表结构，如果需要可以使用SQLAlchemy开发者开源的另外一个软件Alembic来完成。

    步骤三：

    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。

    1、创建表

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    #!/usr/bin/env python
    # -*- coding:utf-8 -*-
    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
     
    engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/t1", max_overflow=5)
     
    Base = declarative_base()
     
    # 创建单表
    class Users(Base):
        __tablename__ = 'users'
        id = Column(Integer, primary_key=True)
        name = Column(String(32))
        extra = Column(String(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(String(50), default='red', unique=True)
     
     
    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"))
     
     
    # 多对多
    class Group(Base):
        __tablename__ = 'group'
        id = Column(Integer, primary_key=True)
        name = Column(String(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(String(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 init_db():
        Base.metadata.create_all(engine)
     
     
    def drop_db():
        Base.metadata.drop_all(engine)

    注：设置外检的另一种方式 ForeignKeyConstraint(['other_id'], ['othertable.other_id'])

    2、操作表

     表结构 + 数据库连接
    • 增
      复制代码
      obj = Users(name="alex0", extra='sb')
session.add(obj)
session.add_all([
    Users(name="alex1", extra='sb'),
    Users(name="alex2", extra='sb'),
])
session.commit()
      复制代码
    • 删
      session.query(Users).filter(Users.id > 2).delete()
session.commit()
    • 改
      session.query(Users).filter(Users.id > 2).update({"name" : "099"})
session.query(Users).filter(Users.id > 2).update({Users.name: Users.name + "099"}, synchronize_session=False)
session.query(Users).filter(Users.id > 2).update({"num": Users.num + 1}, synchronize_session="evaluate")
session.commit()
    • 查
      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()
    • 其他
    #　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
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.sum(Users.id),
    func.min(Users.id)).group_by(Users.name).all()

ret = session.query(
    func.max(Users.id),
    func.sum(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()#默认是inner join

ret = session.query(Person).join(Favor, isouter=True).all()#left join


# 组合
q1 = session.query(Users.name).filter(Users.id > 2)
q2 = session.query(Favor.caption).filter(Favor.nid < 2)
ret = q1.union(q2).all()#去重

q1 = session.query(Users.name).filter(Users.id > 2)
q2 = session.query(Favor.caption).filter(Favor.nid < 2)
ret = q1.union_all(q2).all()#不去重

    更多功能参见文档，猛击这里下载PDF

    完整代码

    创建表

    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

Base = declarative_base()

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

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


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"))



class Group(Base):
    __tablename__ = 'group'
    id = Column(Integer, primary_key=True,autoincrement=True)
    name = Column(String(64), unique=True, nullable=False)

class Server(Base):
    __tablename__ = 'server'

    id = Column(Integer, primary_key=True, autoincrement=True)
    hostname = Column(String(64), unique=True, nullable=False)


def init_db():
    engine = create_engine("mysql+pymysql://root:centos@192.168.147.147:3306/s15day13?charset=utf8", max_overflow=5)
#s15day13数据库名 ?charset=utf8支持中文
    Base.metadata.create_all(engine)

init_db()

    增

    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

Base = declarative_base()

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

engine = create_engine("mysql+pymysql://root:centos@192.168.147.147:3306/s15day13?charset=utf8", max_overflow=5)

Session = sessionmaker(bind=engine)
session = Session()
#单条数据
# obj = Users(name='alex',extra='lowb')
# session.add(obj)
#多条数据
session.add_all([
    Users(name='alex1',extra='lowb1'),
    Users(name='alex2',extra='lowb2'),
    Users(name='alex3',extra='lowb3'),
])
session.commit()

    删

    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

Base = declarative_base()

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

engine = create_engine("mysql+pymysql://root:centos@192.168.147.147:3306/s15day13?charset=utf8", max_overflow=5)

Session = sessionmaker(bind=engine)
session = Session()
session.query(Users).filter(Users.name=='alex').delete()
session.commit()

    改

    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

Base = declarative_base()

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

engine = create_engine("mysql+pymysql://root:centos@192.168.147.147:3306/s15day13?charset=utf8", max_overflow=5)

Session = sessionmaker(bind=engine)
session = Session()
#session.query(Users).filter(Users.id==2,Users.name=="alex1").update({Users.name:"ALEX"})
#session.query(Users).filter(Users.id==2,Users.name=="ALEX").update({'name':"ALEX1"})
#session.query(Users).filter(Users.id==2,Users.name=="ALEX1").update({"name":Users.name + 1},synchronize_session="evaluate")
session.query(Users).filter(Users.id > 2).update({Users.name: Users.name + "099"}, synchronize_session=False)

session.commit()

    查

    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

Base = declarative_base()

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

engine = create_engine("mysql+pymysql://root:centos@192.168.147.147:3306/s15day13?charset=utf8", max_overflow=5)

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

# 获取全部数据
# v = session.query(Users).all()#v是每个对象生成的列表
# for row in v:
   #通过每个对象对应的方法取具体值
    # print(row.id,row.name,row.extra)

# 获取第一条数据
# v = session.query(Users).first()
# print(v)

# session.query(Users).filter(Users.id==2)
# session.query(Users).filter(Users.id==2,Users.name=="root1")
# session.query(Users).filter(Users.id==2)
#
# v = session.query(Users).filter_by(id=2).all()
# print(v)
# 获取指定映射
v = session.query(Users.id,Users.name)#查询sql语句
print(v)

     连表操作

    

    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

    Base = declarative_base()

    class Hobby(Base):
        __tablename__ = 'hobby'
        nid = Column(Integer, primary_key=True)
        caption = Column(String(50), default='red', unique=True)


    class Person(Base):
        __tablename__ = 'person'
        nid = Column(Integer, primary_key=True)
        name = Column(String(32), index=True, nullable=True)
        hobby_id = Column(Integer, ForeignKey("hobby.nid"))
        hobby = relationship("Hobby", backref='persons')

    def init_db():
        engine = create_engine("mysql+pymysql://root:centos@192.168.147.147:3306/s15day13?charset=utf8", max_overflow=5)
        Base.metadata.create_all(engine)


    def drop_db():
        engine = create_engine("mysql+pymysql://root:centos@192.168.147.147:3306/s15day13?charset=utf8", max_overflow=5)
        Base.metadata.drop_all(engine)

    init_db()
    engine = create_engine("mysql+pymysql://root:centos@192.168.147.147:3306/s15day13?charset=utf8", max_overflow=5)

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

    # session.add_all([
    #     Hobby(nid=1,caption='basketball'),
    #     Hobby(nid=2,caption='football'),
    #     Hobby(nid=3,caption='banball')
    # ])
    # session.commit()
    #
    #
    #
    # session.add_all([
    #     Person(nid=1,name='alex1',hobby_id=1),
    #     Person(nid=2,name='alex2',hobby_id=2),
    #     Person(nid=3,name='alex3',hobby_id=1),
    # ])
    # session.commit()
    #傻逼版本的连表操作
    v = session.query(Person.name,Hobby.caption).join(Hobby,isouter=True).all()
    print(v)
    

     
    

    

    便捷版本的连表操作
    

    在person表中加了一个字段hobby，仅仅为了方便连表查询
    

    一对多
    

    

    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

Base = declarative_base()

class Hobby(Base):
    __tablename__ = 'hobby'
    nid = Column(Integer, primary_key=True)
    caption = Column(String(50), default='red', unique=True)


class Person(Base):
    __tablename__ = 'person'
    nid = Column(Integer, primary_key=True)
    name = Column(String(32), index=True, nullable=True)
    hobby_id = Column(Integer, ForeignKey("hobby.nid"))
    hobby = relationship("Hobby", backref='persons')

def init_db():
    engine = create_engine("mysql+pymysql://root:centos@192.168.147.147:3306/s15day13?charset=utf8", max_overflow=5)
    Base.metadata.create_all(engine)


def drop_db():
    engine = create_engine("mysql+pymysql://root:centos@192.168.147.147:3306/s15day13?charset=utf8", max_overflow=5)
    Base.metadata.drop_all(engine)

engine = create_engine("mysql+pymysql://root:centos@192.168.147.147:3306/s15day13?charset=utf8", max_overflow=5)

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

    #正向查询，通过person找hobby
v     = session.query(Person).all()
for obj in v:
    print(obj.nid,obj.name,obj.hobby.caption)#obj代指Person表的每行，obj.hobby指的就是Hobby这个对象
    

    #反向查询，找出所有爱好是篮球的人名
    v = session.query(Person.name,Hobby.caption).join(Hobby,isouter=True).filter(Hobby.caption=='basketball').all()
    print(v)
    #新方式
    v = session.query(Hobby).filter(Hobby.caption=='basketball').all()
    for obj in v:
        print(obj.persons,obj.caption)
    for row in obj.persons:
        print(row.name)
    

     
    

    

    多对多（需要第三表的介入）
    

    傻逼版本
    

    

    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

Base = declarative_base()
class Host(Base):
    __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):
    __tablename__ = 'host_user'
    nid = Column(Integer, primary_key=True, autoincrement=True)
    username = Column(String(32))

class HostToHostUser(Base):
    __tablename__='host_to_hostuser'
    nid = Column(Integer,primary_key=True,autoincrement=True)
    host_id = Column(Integer,ForeignKey('host.nid'))
    host_user_id = Column(Integer,ForeignKey('host_user.nid'))

def init_db():
    engine = create_engine("mysql+pymysql://root:centos@192.168.147.147:3306/s15day13?charset=utf8", max_overflow=5)
    #t1 库名  ?charset=utf8 支持中文
    Base.metadata.create_all(engine)

engine = create_engine("mysql+pymysql://root:centos@192.168.147.147:3306/s15day13?charset=utf8", max_overflow=5)

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

# session.add_all([
#         Host(hostname='nginx1',port='22',ip='192.168.1.1'),
#         Host(hostname='nginx2',port='22',ip='192.168.1.2'),
#         Host(hostname='mysql1',port='22',ip='192.168.1.3'),
#         Host(hostname='mysql2',port='22',ip='192.168.1.4'),
#         Host(hostname='git',port='22',ip='192.168.1.5'),
# ])
# session.commit()
# session.add_all([
#         HostUser(username='alex1'),
#         HostUser(username='alex2'),
#         HostUser(username='alex3'),
#
# ])
# session.commit()
# session.add_all([
#         HostToHostUser(host_id=1,host_user_id=1),
#         HostToHostUser(host_id=1,host_user_id=2),
#         HostToHostUser(host_id=2,host_user_id=1),
# ])
# session.commit()

host_obj = session.query(Host).filter(Host.hostname == 'nginx1').first()#根据主机名找到主机id
host_2_host_user = session.query(HostToHostUser.host_user_id).filter(HostToHostUser.host_id == host_obj.nid).all()#根据主机id找到用户id
r = zip(*host_2_host_user)
users = session.query(HostUser.username).filter(HostUser.nid.in_(list(r)[0])).all()#根据用户id，找到用户名
print(users)
    

    

     牛逼版本1
    

    通过主机名找到有权限的用户，其实就是利用了relationship,在第三张表中和两个表建立关联，只是查询时需要先通过主机名在host表查到满足的主机对象，而此时主机对象中因为第三张表中的relationship，通过h就能访问hosttohostgroup的对象，再通过第三个表中的第二个relationship正向查询到用户名。
    

    

    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

Base = declarative_base()
class Host(Base):
    __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):
    __tablename__ = 'host_user'
    nid = Column(Integer, primary_key=True, autoincrement=True)
    username = Column(String(32))

class HostToHostUser(Base):
    __tablename__='host_to_hostuser'
    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')
def init_db():
    engine = create_engine("mysql+pymysql://root:centos@192.168.147.147:3306/s15day13?charset=utf8", max_overflow=5)
    #t1 库名  ?charset=utf8 支持中文
    Base.metadata.create_all(engine)

engine = create_engine("mysql+pymysql://root:centos@192.168.147.147:3306/s15day13?charset=utf8", max_overflow=5)

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

host_obj = session.query(Host).filter(Host.hostname=='nginx1').first()
# print(host_obj.nid)
# print(host_obj.hostname)
# print(host_obj.port)
#第三张表对应的对象
# print(host_obj.h)
#循环获取的对象
for item in host_obj.h:
    print(item.host_user.username)
    

    

     牛逼版本2
    

    

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

Base = declarative_base()

HostToHostUser = Table('host_to_hostuser',Base.metadata,
                       Column('host_id',ForeignKey('host.nid'),primary_key=True),
                       Column('host_user_id',ForeignKey('host_user.nid'),primary_key=True),)

class Host(Base):
    __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=HostToHostUser,backref='h')

class HostUser(Base):
    __tablename__ = 'host_user'
    nid = Column(Integer, primary_key=True, autoincrement=True)
    username = Column(String(32))



def init_db():
    engine = create_engine("mysql+pymysql://root:centos@192.168.147.147:3306/s15day13?charset=utf8", max_overflow=5)
    #t1 库名  ?charset=utf8 支持中文
    Base.metadata.create_all(engine)

engine = create_engine("mysql+pymysql://root:centos@192.168.147.147:3306/s15day13?charset=utf8", max_overflow=5)

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

host_obj = session.query(Host).filter(Host.hostname=='nginx1').first()

print(host_obj.host_user)
for item in host_obj.host_user:
    print(item.username)
    

    


    

    
    
                
    
                
              
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                原文地址：https://www.cnblogs.com/hongpeng0209/p/6265557.html
              
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