SQLObject和SQLAlchemy入门


#Python#


2014-01-07

SQLObject和SQLAlchemy都是Python语言下的ORM(对象关系映射)解决方案,其中SQLAlchemy被认为是Python下事实上的ORM标准。当然,两者都很优秀。

本文主要记录sqlobject的简单使用。使用Linux Mint 15,Python 2.7。

安装

sudo pip install SQLObject

使用SQLObject操作mysql时候报错ImportError: No module named MySQLdb,那便安装MySQLdb:

sudo pip install MySQL-python

没想到又报错了:

_mysql.c:29:20: fatal error: Python.h: No such file or directory
compilation terminated.
error: command 'x86_64-linux-gnu-gcc' failed with exit status 1

解决方法:

sudo apt-get install libmysqlclient-dev python-dev

使用其创建表

将mysql默认存在的test数据库的编码改为utf-8。

#-*-encoding:utf-8-*-
from sqlobject import *

uri = r'mysql://root:passwd@127.0.0.1/test?charset=utf8'
sqlhub.processConnection = connectionForURI(uri)

class User(SQLObject):
    name = StringCol(length=10, notNone=True)
    email = StringCol(length=20, notNone=True)
    password = StringCol(length=20, notNone=True)

User.createTable()

运行后,会看到test数据库下出现表user,我们使用show create table user;查看user表的创建语句,结果如下:

CREATE TABLE `user` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(10) NOT NULL,
  `email` varchar(20) NOT NULL,
  `password` varchar(20) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8

添加/删除记录

现在我们尝试着添加和删除记录。

user1 = User(name='user1',email='user1@163.com',password='111')
user2 = User(name='user2',email='user2@163.com',password='222')

运行后,使用select * from user能看到这两个记录:

mysql> select * from user;
+----+-------+---------------+----------+
| id | name  | email         | password |
+----+-------+---------------+----------+
|  1 | user1 | user1@163.com | 111      |
|  2 | user2 | user2@163.com | 222      |
+----+-------+---------------+----------+
2 rows in set (0.00 sec)

通过id获取数据:

u1 = User.get(1)
u1_1 = User.get(1)
u2 = User.get(2)
print id(u1), u1
print id(u1_1), u1_1
print id(u2), u2

输出结果:

23864656 
23864656 
23930512 

由于id(u1)id(u1_1)是相等的,所以u1u1_1是内容一致,这样做可以减少内存使用。可以在连接数据库时候设置参数,禁止该方式。

根据name进行查询:

users = User.select(User.q.name=="user1")
print users
print list(users)

输出结果:

SELECT user.id, user.name, user.email, user.password FROM user WHERE ((user.name) = ('user1'))
[]

模糊查询:

users = User.select(User.q.name.startswith('u'))
print users
print list(users)
users = User.select(User.q.name.contains('ser1'))
print users
print list(users)

运行结果:

SELECT user.id, user.name, user.email, user.password FROM user WHERE (user.name LIKE ('u%') ESCAPE '\\')
[, ]
SELECT user.id, user.name, user.email, user.password FROM user WHERE (user.name LIKE ('%ser1%') ESCAPE '\\')
[]

一对多映射

我们新建一个表,保存user中每个用户的编写的文章:

class User(SQLObject):
    name = StringCol(length=10, notNone=True)
    email = StringCol(length=20, notNone=True)
    password = StringCol(length=20, notNone=True)

class Article(SQLObject):
    title = StringCol(length=100, notNone=True)
    content = StringCol(notNone=True)
    user = ForeignKey('User')
Article.createTable()

运行后,使用show create table article查看创建语句:

CREATE TABLE `article` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `title` varchar(100) NOT NULL,
  `content` text NOT NULL,
  `user_id` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `article_user_id_exists` (`user_id`),
  CONSTRAINT `article_user_id_exists` FOREIGN KEY (`user_id`) REFERENCES `user` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8

添加数据:

u1 = User.get(1)
a1 = Article(title='title1',content='你好',user=u1)

查询数据:

u1 = User.get(1)
a1 = Article.select(Article.q.user == u1)
print a1
print list(a1)
print list(a1)[0].content

这种方式也可以:

a1 = Article.select(Article.q.userID == 1)
print a1
print list(a1)
print list(a1)[0].content

运行结果:

SELECT article.id, article.title, article.content, article.user_id FROM article WHERE ((article.user_id) = (1))
[<Article title='title1'>]
你好

删除数据

u2 = User.get(2)
print User.delete(u2.id)

SQLObject相关资料:

SQLAlchemy相关资料:


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