15-Python操做MySQL

本篇对于Python操做MySQL主要使用两种方式：

• 原生模块 pymsql
• ORM框架 SQLAchemy

pymsql

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

下载安装

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1	pip3 install pymysql

使用操做

一、执行SQL

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#!/usr/bin/env python # -*- coding:utf-8 -*- import pymysql    # 建立链接 conn = pymysql. connect (host= '127.0.0.1' , port=3306, user = 'root' , passwd= '123' , db= 't1' ) # 建立游标 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，否则没法保存新建或者修改的数据 conn. commit ()    # 关闭游标 cursor . close () # 关闭链接 conn. close ()

二、获取新建立数据自增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

三、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) # 获取全部数据 # 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

四、fetch数据类型

　　关于默认获取的数据是元祖类型，若是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 ()

 做业： 参考表结构： 用户类型 用户信息 权限 用户类型&权限 功能： # 登录、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

练习题

SQLAchemy

SQLAlchemy是Python编程语言下的一款ORM框架，该框架创建在数据库API之上，使用关系对象映射进行数据库操做，简言之即是：将对象转换成SQL，而后使用数据API执行SQL并获取执行结果。

安装：

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1	pip3 install SQLAlchemy

 

SQLAlchemy自己没法操做数据库，其必须以来pymsql等第三方插件，Dialect用于和数据API进行交流，根据配置文件的不一样调用不一样的数据库API，从而实现对数据库的操做，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

1、内部处理

使用 Engine/ConnectionPooling/Dialect 进行数据库操做，Engine使用ConnectionPooling链接数据库，而后再经过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) # 获取全部数据 # cur.fetchall()

2、ORM功能使用

使用 ORM/Schema Type/SQL Expression Language/Engine/ConnectionPooling/Dialect 全部组件对数据进行操做。根据类建立对象，对象转换成SQL，执行SQL。

一、建立表

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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()   # 建立单表 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：设置外检的另外一种方式 ForeignKeyConstraint(['other_id'], ['othertable.other_id'])

二、操做表

#!/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() # 建立单表
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()

表结构 + 数据库链接

• 增
  

  obj = Users(name="alex0", extra='sb') session.add(obj) session.add_all([ Users(name="alex1", extra='sb'), Users(name="alex2", extra='sb'), ]) session.commit()

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• 删
  

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

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• 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()

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• 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() 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()

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• 其余
  

  #　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()

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