wget http://peak.telecommunity.com/dist/ez_setup.py
 python ez_setup.py
 sudo easy_install sqlalchemy
 sudo easy_install ipython

from django.db import models

class Game(models.Model):
 ... ...

class GameCompany(models.Model):
 ... ...

from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, ForeignKey, Date
from sqlalchemy.orm import relationship, backref

Base = declarative_base()

# 定义表结构
class GameCompany(Base):
 __tablename__ = 'game_company'

 id = Column(Integer, primary_key=True)
 name = Column(String(200), nullable=False)
 country = Column(String(50))


class Game(Base):
 __tablename__ = 'game'

 id = Column(Integer, primary_key=True)
 company_id = Column(Integer, ForeignKey('game_company.id'), index=True)
 category = Column(String(10))
 name = Column(String(200), nullable=False)
 release_date = Column(Date)

 # 和Django不同，外键需要显式定义，具体好坏见仁见智
 # 此处的relation可以为lazy加载外键内容时提供一些可配置的选项
 company = relationship('GameCompany', backref=backref('games'))


# 此处定义要使用的数据库
engine = create_engine('mysql://root:root@localhost:5379/sqlalchemy_tutorial"htmlcode">

nintendo = GameCompany(name="nintendo", country="Japan")
nintendo.save()

game1 = Game(
 company=nintendo,
 category="ACT",
 name="Super Mario Bros",
 release_date='1985-10-18')
game1.save()

# 或者使用create
Game.objects.create(... ...)




（2）SQLAlchemy
在SQLAlchemy ORM中，有一个非常关键的对象 session ，所有对于数据的操作都是 通过session来进行的，所以要插入数据之前，我们得先初始化一个session：


from sqlalchemy.orm import sessionmaker
Session = sessionmaker(bind=engine)
session = Session()



之后插入数据的方法也和Django比较相似：


# 添加数据
nintendo = GameCompany(name="Nintendo", country="Japan")
capcom = GameCompany(name="Capcom", country="Japan")
game1 = Game(
 company=nintendo,
 category="ACT",
 name="Super Mario Bros",
 release_date='1985-10-18'
)
game2 = Game(
 company=capcom,
 category="ACT",
 name="Devil May Cry 3: Dante's Awakening",
 release_date="2005-03-01",
)
game3 = Game(
 company=nintendo,
 category="RPG",
 name="Mario & Luigi: Dream Team",
 release_date="2013-08-11",
)

# 使用add_all来让这些objects和session产生关系
session.add_all([nintendo, capcom, game1, game2])
# 在没有开启autocommit的模式下，不要忘了调用commit来让数据写到数据库中
session.commit()




除了commit之外，session还有rollback()等方法，你可以把session对象简单看成是一次 transaction，所以当你对内容进行修改时，需要调用 session.commit() 来提交这些修改。
去文档可以了解更多session相关内容：http://docs.sqlalchemy.org/en/rel_0_9/orm/session.html
二、常用操作
1.简单查询

（1）批量查询


# -- Django --
Game.objects.filter(category="RPG")

# -- SQLAlchemy --
# 使用filter_by是和django ORM比较接近的方式
session.query(Game).filter_by(category="RPG")
session.query(Game).filter(Game.category == "RPG")




（2）查询单个对象


# -- Django --
Game.objects.get(name="Super Mario Bros")

# -- SQLAlchemy --
session.query(Game).filter_by(name="Super Mario Bros").one()
# `get_objects_or_None()`
session.query(Game).filter_by(name="Super Mario Bros").scalar()




Django中得各种 > 、< 都是使用在字段名称后面追加 "__gt"、"__lt" 来实现的，在SQLAlchemy 中这样的查询还要更直观一些


# -- Django --
Game.objects.filter(release_date__gte='1999-01-01')
# 取反
Game.objects.exclude(release_date__gte='1999-01-01')

# -- SQLAlchemy --
session.query(Game).filter(Game.release_date >= '1999-01-01').count()
# 取反使用 ~ 运算符
session.query(Game).filter(~Game.release_date >= '1999-01-01').count()
通过外键组合查询

# -- Django --
Game.objecs.filter(company__name="Nintendo")

# -- SQLAlchemy --
session.query(Game).join(GameCompany).filter(GameCompany.name == "Nintendo")




2.多条件或查询


# -- Django --
from django.db.models import Q
Game.objects.filter(Q(category="RPG") | Q(category="ACT"))

# -- SQLAlchemy --
from sqlalchemy import or_
session.query(Game).filter(or_(Game.category == "RPG", Game.category == "ACT"))
session.query(Game).filter((Game.category == "RPG") | (Game.category == "ACT"))




（1）in查询


# -- Django --
Game.objects.filter(category__in=["GAL", "ACT"])

# -- SQLAlchemy --
session.query(Game).filter(Game.category.in_(["GAL", "ACT"]))




（2）like查询


# -- Django --
Game.objects.filter(name__contains="Mario")

# -- SQLAlchemy --
session.query(Game.name.contains('Mario'))




3.统计个数
简单统计总数：


# -- Django --
Game.objects.filter(category="RPG").count()

# -- SQLAlchemy --
session.query(Game).filter_by(category="RPG").count()
分组统计个数

# -- Django --
from django.db.models import Count
Game.objects.values_list('category').annotate(Count('pk')).order_by()

# -- SQLAlchemy --
from sqlalchemy import func
session.query(Game.category, func.count(Game.category)).group_by(Game.category).all()




4.结果排序
对查询结果进行排序：


# -- Django --
Game.objects.all().order_by('release_date')
Game.objects.all().order_by('-release_date')
# 多字段排序
Game.objects.all().order_by('-release_date', 'category')

# -- SQLAlchemy --
session.query(Game).order_by(Game.release_date)
session.query(Game).order_by(Game.release_date.desc())
# 多字段排序
session.query(Game).order_by(Game.release_date.desc(), Game.category)




5.修改数据


# -- Django --
game = Game.objects.get(pk=1)
game.name = 'Super Mario Brothers'
game.save()

# -- SQLAlchemy --
game = session.query(Game).get(1)
game.name = 'Super Mario Brothers'
session.commit()




6.批量修改


# -- Django --
Game.objects.filter(category="RPG").update(category="ARPG")

# -- SQLAlchemy --
session.query(Game).filter_by(category="RPG").update({"category": "ARPG"})




7.批量删除


# -- Django --
Game.objects.filter(category="ARPG").delete()

# -- SQLAlchemy --
session.query(Game).filter_by(category="ARPG").delete()




三、SQLAlchemy其他一些值得关注的功能

上面简单列了一些SQLAlchemy ORM和Django ORM的使用方法对比，SQLAlchemy同时还提供了一些 其他非常有用的功能，比如Automap~
假如你有一个Django项目，通过ORM创建了一大堆Model。这时来了一个新项目，需要操作 这些表，应该怎么办？拷贝这些Models？使用原始的DB-API加上sql来操作？
其实使用SQLAlchemy的Automap可以让你的工作变得非常的方便，你只要在新项目连接到旧数据库，然后 稍微配置一下Automap，就可以使用SQLAlchemy的ORM操作那些通过别的系统创建的表了。
就像这样：


from sqlalchemy.ext.automap import automap_base
from sqlalchemy.orm import Session
from sqlalchemy import create_engine

Base = automap_base()
engine = create_engine("sqlite:///mydatabase.db")
Base.prepare(engine, reflect=True)

# user和address就是表明，通过这样的语句就可以把他们分别映射到User和Address类
User = Base.classes.user
Address = Base.classes.address




更多信息可以参考详细文档：http://docs.sqlalchemy.org/en/rel_0_9/orm/extensions/automap.html
附：Django与SQLAlchemy结合的实例演示

譬如，以下gumi/db.py代码，其中gumi制作Django项目名，项目中使用的唯一的数据库连接的包装，作为py调用。




# -*- coding: utf-8 -*- 
from django.conf import settings 
from django.core import signals 
from django.dispatch import dispatcher 
import sqlalchemy 
from sqlalchemy.orm import scoped_session, sessionmaker 
from sqlalchemy.engine.url import URL 
 
__all__ = ['Session', 'metadata'] 
 
def create_engine(): 
 url = URL(drivername=settings.DATABASE_ENGINE, 
    database=settings.DATABASE_NAME, 
    username=settings.DATABASE_USER, 
    password=settings.DATABASE_PASSWORD, 
    host=settings.DATABASE_HOST, 
    port=settings.DATABASE_PORT or None, 
    query = getattr(settings, 'DATABASE_OPTIONS', {}) 
    ) 
 
 options = getattr(settings, 'SQLALCHEMY_OPTIONS', {}) 
 engine = sqlalchemy.create_engine(url, **options) 
 return engine 
 
def end_request(signal, sender): 
 Session.remove() 
 
dispatcher.connect(receiver=end_request, 
     signal=signals.request_finished) 
 
metadata = sqlalchemy.MetaData() 
 
Session = scoped_session(sessionmaker(autoflush=True, 
          transactional=True, 
          bind=create_engine())) 



模块代码




from sqlalchemy.orm import * 
from gumi.db import Session, metadata 
some_table = Table('some_table', metadata, 
       Column('id', Integer, primary_key=True), 
       Column('some_value', String(100), nullable=False, 
       mysql_engine='InnoDB', 
       ) 
class SomeObject(object): 
 pass 
mapper(SomeObject, some_table) 



视图代码




import django.newforms as forms 
from gumi.db import Session 
 
class SomeForm(forms.Form): 
  # newform 
  pass 
 
def some_action(req): 
  if req.method != "POST": 
   form = SomeForm() 
  else: 
   form = SomeForm(req.POST) 
   if form.is_valid(): 
     data = form.clean() 
     obj = SomeObject() 
     obj.some_param = data['a'] 
     obj.another_param = data['b'] 
     Session.save(obj) 
     Session.commit() 
     return HttpResponseRedirect('/') 
  return render_to_response('some/template.html')