Python SQLAlchemy 程序实例

Sample1

# coding=gbk

from sqlalchemy import *
from sqlalchemy.orm import *

engine = create_engine('sqlite:///./sqlalchemy.db', echo=True)
metadata = MetaData(engine)

'''
create table
'''
users_table = Table('users',
                    metadata,
                    Column('id', Integer, primary_key=True),
                    Column('name', String(40)),
                    Column('email', String(120)))
if not users_table.exists():
    users_table.create()

'''
load table
'''
users_table = Table('users', metadata, autoload=True)

'''
insert
'''
users_table.insert().execute(name="sss", email="[email protected]")
users_table.insert().execute(name="ttt", email="[email protected]")
'''
update
'''
users_table.update(users_table.c.name=="ttt").execute(name="ddd")

'''
select
'''
result=users_table.select(and_(users_table.c.name == "ddd", users_table.c.email == "[email protected]")).execute()
for item in result.fetchall():
    print item

'''
delete
'''
users_table.delete(users_table.c.name=="ddd").execute()

'''
ORM -- bind
'''
class User(object):
    pass
mapper(User, users_table) 

Session = sessionmaker() #创建了一个自定义了的 Session类
Session.configure(bind=engine)  #将创建的数据库连接关联到这个session
session = Session()
u = User()
u.name='asdf'
u.email='[email protected]'
session.add(u)  #在session中添加内容

session.flush() #保存数据
session.commit() #数据库事务的提交,sisson自动过期而不需要关闭

Sample2

# coding=gbk

from sqlalchemy.orm import mapper, sessionmaker #sessionmaker() 函数是最常使用的创建最顶层可用于整个应用 Session 的方法,Session 管理着所有与数据库之间的会话
from datetime import datetime
from sqlalchemy import Table, MetaData, Column, ForeignKey, Integer, String, Unicode, DateTime #会SQL的人能理解这些函数吧?
from sqlalchemy import *
from sqlalchemy.orm import *

engine = create_engine("sqlite:///tutorial.db", echo=True) #创建到数据库的连接,echo=True 表示用logging输出调试结果
metadata = MetaData() #跟踪表属性
user_table = Table( #创建一个表所需的信息:字段,表名等
                    'tf_user', metadata,
                    Column('id', Integer, primary_key=True),
                    Column('user_name', Unicode(16), unique=True, nullable=False),
                    Column('email_address', Unicode(255), unique=True, nullable=False),
                    Column('password', Unicode(40), nullable=False),
                    Column('first_name', Unicode(255), default=''),
                    Column('last_name', Unicode(255), default=''),
                    Column('created', DateTime, default=datetime.now))
metadata.create_all(engine)  #在数据库中生成表
class User(object): pass #创建一个映射类
mapper(User, user_table) #把表映射到类
Session = sessionmaker() #创建了一个自定义了的 Session类
Session.configure(bind=engine)  #将创建的数据库连接关联到这个session
session = Session()
u = User()
u.user_name='dongwm'
u.email_address='[email protected]'
u.password='testpass'  #给映射类添加以下必要的属性,因为上面创建表指定这几个字段不能为空
session.add(u)  #在session中添加内容

session.flush() #保存数据
session.commit() #数据库事务的提交,sisson自动过期而不需要关闭

query = session.query(User) #query() 简单的理解就是select() 的支持 ORM 的替代方法,可以接受任意组合的 class/column 表达式
print list(query) #列出所有user
print query.get(1) #根据主键显示
print query.filter_by(user_name='dongwm').first()  #类似于SQL的where,打印其中的第一个
u = query.filter_by(user_name='dongwm').first()
u.password = 'newpass' #修改其密码字段
session.commit() #提交事务
print query.get(1).password #打印会出现新密码

for instance in session.query(User).order_by(User.id):  #根据id字段排序,打印其中的用户名和邮箱地址
    print instance.user_name, instance.email_address

Sample3:

# coding=gbk

from sqlalchemy import *
from sqlalchemy.orm import *
from datetime import datetime
from sqlalchemy import Table, MetaData, Column, ForeignKey, Integer, String, Unicode, DateTime

engine = create_engine("sqlite:///tutorial2.db", echo=True) #创建到数据库的连接,echo=True 表示用logging输出调试结果
metadata = MetaData() #跟踪表属性

class User(object):
    pass

class Group(object):
    pass

class Permission(object):
    pass

user_table = Table('tf_user',
                   metadata,
                   Column('id', Integer, primary_key=True),
                   Column('user_name', Unicode(16), unique=True, nullable = False),
                   Column('password', Unicode(16), nullable = False))

group_table = Table("tf_group",
                    metadata,
                    Column('id', Integer, primary_key=True),
                    Column('group_name', Unicode(16), unique=True, nullable = False))

permission_table = Table("tf_permission",
                    metadata,
                    Column('id', Integer, primary_key=True),
                    Column('permission_name', Unicode(16), unique=True, nullable = False))

user_group = Table("user_group",
                   metadata,
                   Column('user_id', None, ForeignKey('tf_user.id'), primary_key=True),
                   Column('group_id', None, ForeignKey('tf_group.id'), primary_key=True))

group_permission = Table("group_permission",
                   metadata,
                   Column('permission_id', None, ForeignKey('tf_permission.id'), primary_key=True),
                   Column('group_id', None, ForeignKey('tf_group.id'), primary_key=True))

mapper(User, user_table, properties=dict(_groups=relation(Group, secondary=user_group, backref='_users')))
mapper(Group, group_table, properties=dict(_permissions=relation(Permission, secondary=group_permission, backref='_groups')))
mapper(Permission, permission_table)

metadata.create_all(engine)