python成长之路13
一：SqlAlchemy ORM
ORM：Object Relational Mapping 对象关系映射是一种程序技术，用于实现面向对象编程语言里不同类型系统的数据之间的转换
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：
建立在SQL AQI至上，不需要写原生SQL语句，是将对象封装并转成原生语句
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：
MySQL-Python #适用于python 2使用MySQL-python模块
mysql+mysqldb://<user>:<password>@<host>[:<port>]/<dbname>
pymysql #适用于python 3，因为python 3里面的mysql模块变为pymysql
mysql+pymysql://<username>:<password>@<host>/<dbname>[?<options>]
MySQL-Connector #使用mysql connector连接数据库
mysql+mysqlconnector://<user>:<password>@<host>[:<port>]/<dbname>
cx_Oracle #连接到oracle数据库
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、使用 sqlalchemy + pymysql创建表：
import pymysql
from sqlalchemy import create_engine, Table, Column, Integer, String, MetaData, ForeignKey
metadata = MetaData()
#创建user和color两个表，metadata封装语句
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+pymysql://root:zhang@123@localhost:3306/test", max_overflow=5) #连接到数据库，最大连接池5个
metadata.create_all(engine) #创建数据库
2、增加数据：
import pymysql
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+pymysql://root:zhang@123@localhost:3306/test", max_overflow=5)
conn = engine.connect()
sql = user.insert().values(id=1,name='wu') #id可以不写，会自增
conn.execute(sql)
conn.close()
数据库验证：
3、删除数据：
#/usr/bin/env python
# -*- coding:utf-8 -*-
import pymysql
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+pymysql://root:zhang@123@localhost:3306/test", max_overflow=5)
conn = engine.connect()
sql1 = user.delete().where(user.c.id == 1) #匹配id为1
sql2 = user.delete().where(user.c.name == 'li') #匹配条件name为li
conn.execute(sql1) #执行语句
conn.execute(sql2)
conn.close()
4、改数据：
import pymysql
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+pymysql://root:zhang@123@localhost:3306/test", max_overflow=5)
conn = engine.connect()
#sql1 = user.insert().values(name="zhang") #添加数据
sql1 = user.update().where(user.c.name == 'zhang').values(name='jack') #匹配套件并改数据
conn.execute(sql1)
conn.close()
5、查数据：
#/usr/bin/env python
# -*- coding:utf-8 -*-
import pymysql
from sqlalchemy import create_engine, select,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+pymysql://root:zhang@123@localhost:3306/test", max_overflow=5)
conn = engine.connect()
sql = select([user,])
res = conn.execute(sql)
print(res.fetchall())
conn.close()
实际使用方法介绍：
创建表并插入数据：
#/usr/bin/env python
# -*- coding:utf-8 -*-
from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String
from sqlalchemy.orm import sessionmaker
Base = declarative_base() #生成一个SqlORM 基类
engine = create_engine("mysql+pymysql://root:zhang@123@localhost:3306/test",echo=True)
class Host(Base):
__tablename__ = 'hosts'
id = Column(Integer,primary_key=True,autoincrement=True)
hostname = Column(String(64),unique=True,nullable=False)
ip_addr = Column(String(128),unique=True,nullable=False)
port = Column(Integer,default=22)
Base.metadata.create_all(engine) #创建所有表结构
if __name__ == '__main__':
SessionCls = sessionmaker(bind=engine) #创建与数据库的会话session class ,注意,这里返回给session的是个class,不是实例
session = SessionCls()
h1 = Host(hostname='localhost',ip_addr='127.0.0.1')
h2 = Host(hostname='Centos',ip_addr='192.168.10.254',port=2021)
session.add_all([h1,h2])
session.commit() #提交
查询并更改数据：
#/usr/bin/env python
# -*- coding:utf-8 -*-
from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String
from sqlalchemy.orm import sessionmaker
Base = declarative_base() #生成一个SqlORM 基类
engine = create_engine("mysql+pymysql://root:zhang@123@localhost:3306/test",echo=True)
class Host(Base):
__tablename__ = 'hosts'
id = Column(Integer,primary_key=True,autoincrement=True)
hostname = Column(String(64),unique=True,nullable=False)
ip_addr = Column(String(128),unique=True,nullable=False)
port = Column(Integer,default=22)
Base.metadata.create_all(engine) #创建所有表结构
if __name__ == '__main__':
SessionCls = sessionmaker(bind=engine) #创建与数据库的会话session class ,注意,这里返回给session的是个class,不是实例
session = SessionCls()
h1 = Host(hostname='localhost',ip_addr='127.0.0.1')
h2 = Host(hostname='Centos',ip_addr='192.168.10.254',port=2021)
session.add_all([h1,h2])
#session.rollback()
#h3 = Host(hostname='ubuntu2',ip_addr='192.168.2.244',port=20000)
#session.add(h3)
#session.add_all( [h1,h2])
#h2.hostname = 'ubuntu_test' #只要没提交,此时修改也没问题
res = session.query(Host).filter(Host.hostname.in_(['ubuntu2','localhost'])).first() #all所有，first第一个，last最后一个
#res.hostname = "test hostname" #将查到的数据改值
session.delete(res) #删除查询到的数据
session.commit() #提交
ORM 外键关联多对多: 一个组可以包含多个主机，一个主机也可以在多个组，即一个主机可以在多个组里面，如下：
class Parent(Base): #父类
__tablename__ = 'parent'
id = Column(Integer, primary_key=True)
children = relationship("Child")
class Child(Base): #子类
__tablename__ = 'child' #定义表名称
id = Column(Integer, primary_key=True) #id的值类型
parent_id = Column(Integer, ForeignKey('parent.id')) #关联父类的'parent.id即可完成与父类的外键关联
测试；
sqlalchemy无法在已经存在的表里面增加新的字段，因此可以将表删除重新创建，或自己使用原生SQL语句创建，也可以使用sqlalchemy的三方工具，我们这里将以前的表删除再重建：
mysql> drop tables hosts; Query OK, 0 rows affected (0.22 sec)
Pyhton 代码：
#/usr/bin/env python
# -*- coding:utf-8 -*-
from sqlalchemy import create_engine,ForeignKey
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String
from sqlalchemy.orm import sessionmaker
Base = declarative_base() #生成一个SqlORM 基类
engine = create_engine("mysql+pymysql://root:zhang@123@localhost:3306/test",echo=True)
class Host(Base):
__tablename__ = 'hosts'
id = Column(Integer,primary_key=True,autoincrement=True)
hostname = Column(String(64),unique=True,nullable=False)
ip_addr = Column(String(128),unique=True,nullable=False)
port = Column(Integer,default=22)
group_id = Column(Integer, ForeignKey('group.id'))
class Group(Base):
__tablename__ = 'group'
id = Column(Integer,primary_key=True)
name = Column(String(64),unique=True,nullable=False)
child_id = Column(Integer)
Base.metadata.create_all(engine) #创建所有表结构
if __name__ == '__main__':
SessionCls = sessionmaker(bind=engine) #创建与数据库的会话session class ,注意,这里返回给session的是个class,不是实例
session = SessionCls()
session.commit() #提交
验证：
mysql> desc hosts; +----------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +----------+--------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | hostname | varchar(64) | NO | UNI | NULL | | | ip_addr | varchar(128) | NO | UNI | NULL | | | port | int(11) | YES | | NULL | | | group_id | int(11) | YES | MUL | NULL | | +----------+--------------+------+-----+---------+----------------+ 5 rows in set (0.01 sec)
#group_id 行的Key的值是Mul
查看group表：
mysql> desc test.group; +----------+-------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +----------+-------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | name | varchar(64) | NO | UNI | NULL | | | child_id | int(11) | YES | | NULL | | +----------+-------------+------+-----+---------+----------------+ 3 rows in set (0.01 sec)
创建关联的数据：
#/usr/bin/env python
# -*- coding:utf-8 -*-
from sqlalchemy import create_engine,ForeignKey
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String
from sqlalchemy.orm import sessionmaker
Base = declarative_base() #生成一个SqlORM 基类
engine = create_engine("mysql+pymysql://root:zhang@123@localhost:3306/test",echo=True)
class Host(Base):
__tablename__ = 'hosts'
id = Column(Integer,primary_key=True,autoincrement=True)
hostname = Column(String(64),unique=True,nullable=False)
ip_addr = Column(String(128),unique=True,nullable=False)
port = Column(Integer,default=22)
group_id = Column(Integer, ForeignKey('group.id'))
class Group(Base):
__tablename__ = 'group'
id = Column(Integer,primary_key=True)
name = Column(String(64),unique=True,nullable=False)
child_id = Column(Integer)
Base.metadata.create_all(engine) #创建所有表结构
if __name__ == '__main__':
SessionCls = sessionmaker(bind=engine) #创建与数据库的会话session class ,注意,这里返回给session的是个class,不是实例
session = SessionCls()
g3 = Group(name='g3')
session.add_all([g3,])
h1 = Host(hostname='localhost',ip_addr='1.1.1.1',group_id=g3.id) #由于数据库还没有g3的内容，所以这样关联不成功
session.add_all([h1,])
session.commit() #提交
更改关联数据：
#/usr/bin/env python
# -*- coding:utf-8 -*-
from sqlalchemy import create_engine,ForeignKey
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String
from sqlalchemy.orm import sessionmaker
Base = declarative_base() #生成一个SqlORM 基类
engine = create_engine("mysql+pymysql://root:zhang@123@localhost:3306/test",echo=True)
class Host(Base):
__tablename__ = 'hosts'
id = Column(Integer,primary_key=True,autoincrement=True)
hostname = Column(String(64),unique=True,nullable=False)
ip_addr = Column(String(128),unique=True,nullable=False)
port = Column(Integer,default=22)
group_id = Column(Integer, ForeignKey('group.id'))
class Group(Base):
__tablename__ = 'group'
id = Column(Integer,primary_key=True)
name = Column(String(64),unique=True,nullable=False)
child_id = Column(Integer)
Base.metadata.create_all(engine) #创建所有表结构
if __name__ == '__main__':
SessionCls = sessionmaker(bind=engine) #创建与数据库的会话session class ,注意,这里返回给session的是个class,不是实例
session = SessionCls()
g3 = session.query(Group).filter(Group.name=='g3').first() #查到一个已经存在的组
h = session.query(Host).filter(Host.hostname=='localhost').update({'group_id': g3.id}) #查到一个主机的信息并更新其group_id为上一步查到的组的id，即完成了外键的管理
session.commit() #提交
