python orm框架sqlalchemy_Python的ORM框架SQLAlchemy入门教程

SQLAlchemy的核心理念是，SQL数据库查询的数量级和特性关键于目标结合；而目标结合的抽象性又关键于表和行。

一 安裝 SQLAlchemy

编码以下:pip install sqlalchemy

导进要是没有出错则安裝取得成功

编码以下: import sqlalchemy

sqlalchemy.__version__

‘0.9.1’

二 应用 sqlalchemy对数据库操作

1. 界定元信息内容，关联到模块

编码以下:

(env)ghost@ghost-H61M-S2V-B3:~/project/flask/fsql$ python

Python 2.7.3 (default, Apr 10 2013, 05:13:16)

[GCC 4.7.2] on linux2

Type “help”, “copyright”, “credits” or “license” for more information.

from sqlalchemy import *

from sqlalchemy.orm import *

engine = create_engine(‘sqlite:///./sqlalchemy.db’, echo=True) # 界定模块

metadata = MetaData(engine) # 关联元信息内容

2.创建表格，复位数据库查询

编码以下:

users_table = Table(‘users’, metadata,

… Column(‘id’, Integer, primary_key=True),

… Column(‘name’, String(40)),

… Column(’email’, String(120)))

users_table.create()

2014-01-09 10:03:32,436 INFO sqlalchemy.engine.base.Engine

CREATE TABLE users (

id INTEGER NOT NULL,

name VARCHAR(40),

email VARCHAR(120),

PRIMARY KEY (id)

)

2014-01-09 10:03:32,436 INFO sqlalchemy.engine.base.Engine ()

2014-01-09 10:03:32,575 INFO sqlalchemy.engine.base.Engine COMMIT

实行所述编码，大家就建立 一个 users 表，有id， name， email 三个字段

编码以下:

(env)ghost@ghost-H61M-S2V-B3:~/project/flask/fsql$ sqlite3 sqlalchemy.db

SQLite version 3.7.13 2012-06-11 02:05:22

Enter “.help” for instructions

Enter SQL statements terminated with a “;”

sqlite .tables

users

sqlite

3. 操作过程，插进

假如早已table表早已存有， 第二次运作就不能要 create了， 应用 autoload 设定

编码以下:

from sqlalchemy import *

from sqlalchemy.orm import *

engine = create_engine(‘sqlite:///./sqlalchemy.db’, echo=True)

metadata = MetaData(engine)

users_table = Table(‘users’, metadata, autoload=True)

2014-01-09 10:20:01,580 INFO sqlalchemy.engine.base.Engine PRAGMA table_info(“users”)

2014-01-09 10:20:01,581 INFO sqlalchemy.engine.base.Engine ()

2014-01-09 10:20:01,582 INFO sqlalchemy.engine.base.Engine PRAGMA foreign_key_list(“users”)

2014-01-09 10:20:01,583 INFO sqlalchemy.engine.base.Engine ()

2014-01-09 10:20:01,583 INFO sqlalchemy.engine.base.Engine PRAGMA index_list(“users”)

2014-01-09 10:20:01,583 INFO sqlalchemy.engine.base.Engine ()

users_table

Table(‘users’, MetaData(bind=Engine(sqlite:///./sqlalchemy.db)), Column(‘id’, INTEGER(), table=users, primary_key=True, nullable=False), Column(‘name’, VARCHAR(length=40), table=users), Column(’email’, VARCHAR(length=120), table=users), schema=None)

实例化一个插进句柄

编码以下:

i = users_table.insert()

i

sqlalchemy.sql.dml.Insert object at 0x31bc850

print i

INSERT INTO users (id, name, email) VALUES (?, ?, ?)

i.execute(name=’rsj217′, email=’[email protected]’)

2014-01-09 10:24:02,250 INFO sqlalchemy.engine.base.Engine INSERT INTO users (name, email) VALUES (?, ?)

2014-01-09 10:24:02,250 INFO sqlalchemy.engine.base.Engine (‘rsj217’, ‘[email protected]’)

2014-01-09 10:24:02,251 INFO sqlalchemy.engine.base.Engine COMMIT

sqlalchemy.engine.result.ResultProxy object at 0x31bce10

i.execute({‘name’: ‘ghost’},{‘name’: ‘test’})

2014-01-09 10:24:57,537 INFO sqlalchemy.engine.base.Engine INSERT INTO users (name) VALUES (?)

2014-01-09 10:24:57,537 INFO sqlalchemy.engine.base.Engine ((‘ghost’,), (‘test’,))

2014-01-09 10:24:57,537 INFO sqlalchemy.engine.base.Engine COMMIT

sqlalchemy.engine.result.ResultProxy object at 0x31bcd50

数据库查询內容为

编码以下:

sqlite select * from users;

1|rsj217|[email protected]

2|ghost|

3|test|

sqlite

查看 删掉和插进相近 都必须先案例一个 sqlalchemy.sql.dml 目标

三 应用 ORM

应用 orm 便是 将 python class 与 数据库查询的 table 投射，免除立即写 sql 句子

建立投射

编码以下:

class User(object):

… def __repr__(self):

… return ‘%s(%r, %r)’ % (self.__class__.__name__, self.name, self.email)

…

mapper(User, users_table) # 建立投射

Mapper at 0x31bcfd0; User

ul = User()

ul.name

print ul

User(None, None)

print ul.name

None

创建对话

查看

编码以下:

session = create_session()

session

sqlalchemy.orm.session.Session object at 0x31bef10

query = session.query(User)

query

sqlalchemy.orm.query.Query object at 0x31bee50

u = query.filter_by(name=’rsj217′).first()

2014-01-09 10:44:23,809 INFO sqlalchemy.engine.base.Engine SELECT users.id AS users_id, users.name AS users_name, users.email AS users_email

FROM users

WHERE users.name = ?

LIMIT ? OFFSET ?

2014-01-09 10:44:23,809 INFO sqlalchemy.engine.base.Engine (‘rsj217’, 1, 0)

u.name

u’rsj217′

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