Python SQLAlchemy 程序实例

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Sample1

# coding=gbkfrom 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="eee@eee.com")users_table.insert().execute(name="ttt", email="tt@eee.com")'''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 == "tt@eee.com")).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sessionsession = Session()u = User()u.name='asdf'u.email='asdf@asdf.com'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=gbkfrom 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 datetimefrom 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sessionsession = Session()u = User()u.user_name='dongwm'u.email_address='dongwm@dongwm.com'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userprint 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=gbkfrom sqlalchemy import *from sqlalchemy.orm import *from datetime import datetimefrom sqlalchemy import Table, MetaData, Column, ForeignKey, Integer, String, Unicode, DateTimeengine = 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):    passclass Group(object):    passclass Permission(object):    passuser_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)

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