• Python操作MySQL

    本篇对于Python操作MySQL主要使用两种方式：

    • 原生模块 pymsql
    • ORM框架 SQLAchemy

    pymsql

    pymsql是Python中操作MySQL的模块，其使用方法和MySQLdb几乎相同。

    下载安装

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    pip3 install pymysql

    使用操作

    1、执行SQL

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    #!/usr/bin/env python
    # -*- coding:utf-8 -*-
    import pymysql
      
    # 创建连接
    conn = pymysql.connect(host='127.0.0.1', port=3306, user='root', passwd='123', db='t1')
    # 创建游标
    cursor = conn.cursor()
      
    # 执行SQL，并返回收影响行数
    effect_row = cursor.execute("update hosts set host = '1.1.1.2'")
      
    # 执行SQL，并返回受影响行数
    #effect_row = cursor.execute("update hosts set host = '1.1.1.2' where nid > %s", (1,))
      
    # 执行SQL，并返回受影响行数
    #effect_row = cursor.executemany("insert into hosts(host,color_id)values(%s,%s)", [("1.1.1.11",1),("1.1.1.11",2)])
      
      
    # 提交，不然无法保存新建或者修改的数据
    conn.commit()
      
    # 关闭游标
    cursor.close()
    # 关闭连接
    conn.close()

    2、获取新创建数据自增ID

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    #!/usr/bin/env python
    # -*- coding:utf-8 -*-
    import pymysql
      
    conn = pymysql.connect(host='127.0.0.1', port=3306, user='root', passwd='123', db='t1')
    cursor = conn.cursor()
    cursor.executemany("insert into hosts(host,color_id)values(%s,%s)", [("1.1.1.11",1),("1.1.1.11",2)])
    conn.commit()
    cursor.close()
    conn.close()
      
    # 获取最新自增ID
    new_id = cursor.lastrowid

    3、获取查询数据

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    #!/usr/bin/env python
    # -*- coding:utf-8 -*-
    import pymysql
      
    conn = pymysql.connect(host='127.0.0.1', port=3306, user='root', passwd='123', db='t1')
    cursor = conn.cursor()
    cursor.execute("select * from hosts")
      
    # 获取第一行数据
    row_1 = cursor.fetchone()
      
    # 获取前n行数据
    # row_2 = cursor.fetchmany(3)
    # 获取所有数据
    # row_3 = cursor.fetchall()
      
    conn.commit()
    cursor.close()
    conn.close()

    注：在fetch数据时按照顺序进行，可以使用cursor.scroll(num,mode)来移动游标位置，如：

    • cursor.scroll(1,mode='relative')  # 相对当前位置移动
    • cursor.scroll(2,mode='absolute') # 相对绝对位置移动

    4、fetch数据类型

    　　关于默认获取的数据是元祖类型，如果想要或者字典类型的数据，即：

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    #!/usr/bin/env python
    # -*- coding:utf-8 -*-
    import pymysql
      
    conn = pymysql.connect(host='127.0.0.1', port=3306, user='root', passwd='123', db='t1')
      
    # 游标设置为字典类型
    cursor = conn.cursor(cursor=pymysql.cursors.DictCursor)
    r = cursor.execute("call p1()")
      
    result = cursor.fetchone()
      
    conn.commit()
    cursor.close()
    conn.close()
    复制代码
        作业：
        参考表结构：
            用户类型

            用户信息

            权限

            用户类型&权限
        功能：

            # 登陆、注册、找回密码
            # 用户管理
            # 用户类型
            # 权限管理
            # 分配权限

        特别的：程序仅一个可执行文件
    复制代码

    SQLAchemy

    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。

    安装：

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    pip3 install 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，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

    一、内部处理

    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+pymysql://root:123@127.0.0.1:3306/t1", max_overflow=5)
      
    # 执行SQL
    # cur = engine.execute(
    #     "INSERT INTO hosts (host, color_id) VALUES ('1.1.1.22', 3)"
    # )
      
    # 新插入行自增ID
    # cur.lastrowid
      
    # 执行SQL
    # cur = engine.execute(
    #     "INSERT INTO hosts (host, color_id) VALUES(%s, %s)",[('1.1.1.22', 3),('1.1.1.221', 3),]
    # )
      
      
    # 执行SQL
    # cur = engine.execute(
    #     "INSERT INTO hosts (host, color_id) VALUES (%(host)s, %(color_id)s)",
    #     host='1.1.1.99', color_id=3
    # )
      
    # 执行SQL
    # cur = engine.execute('select * from hosts')
    # 获取第一行数据
    # cur.fetchone()
    # 获取第n行数据
    # cur.fetchmany(3)
    # 获取所有数据
    # cur.fetchall()

    二、ORM功能使用

    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。

    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

    复制代码
    #!/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'),
    )

    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(String(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 init_db():
    Base.metadata.create_all(engine)


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


Session = sessionmaker(bind=engine)
session = Session()
    复制代码
    • 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
      复制代码
      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()
      复制代码
    • 查
      复制代码
      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()

ret = session.query(Users).filter(text("id<:value and name=:name")).params(value=224, name='fred').order_by(User.id).all()

ret = session.query(Users).from_statement(text("SELECT * FROM users where name=:name")).params(name='ed').all()
      复制代码
    • 其他
      复制代码
      #　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()

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


# 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()

q1 = session.query(Users.name).filter(Users.id > 2)
q2 = session.query(Favor.caption).filter(Favor.nid < 2)
ret = q1.union_all(q2).all()
      复制代码

    更多功能参见文档，猛击这里下载PDF
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  • 原文地址：https://www.cnblogs.com/nuomin/p/8954939.html
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