django数据库模型

1.在pyCharm中终端执行如下命令创建app

 python manage.py startapp books

2. 在models.py中编写模型代码

from django.db import models

# Create your models here.


class Publisher(models.Model):
    name = models.CharField(max_length=30)
    address = models.CharField(max_length=50)
    city = models.CharField(max_length=60)
    state_province = models.CharField(max_length=30)
    country = models.CharField(max_length=50)
    website = models.URLField()

    def __unicode__(self):
        return self.name

    class Meta:
        ordering = [‘name‘]


class Author(models.Model):
    first_name = models.CharField(max_length=30)
    last_name = models.CharField(max_length=40)
    email = models.EmailField()

    def __unicode__(self):
        return ‘%s %s‘ % (self.first_name, self.last_name)


class Book(models.Model):
    title = models.CharField(max_length=100)
    author = models.ManyToManyField(Author)
    publisher = models.ForeignKey(Publisher)
    publication_date = models.DateField()

    def __unicode__(self):
        return self.title

备注： class Meta表示模型的元信息，eg. 缺省排序； __unicode__方法可以进行任何处理来返回一个对象的字符串表示，类似java中的toString()

3. 校验模型的合法性--语法和逻辑是否正确

python manage.py validate

4. 打印出sql（可以查看django模型与建表sql的对应关系）

python manage.py sqlall books

此时数据库并没有创建任何表

5. 创建表

python manage.py syncdb

6. 登录数据库命令行客户端

python manage.py dbshell  (django根据配置文件中配置的数据库信息，自动检测使用不同的命令行客户端)

#########################################################################

如何利用django提供的API进行CRUD操作呢？

1. 创建对象

p1 = Publisher(name="O‘Reilly", address=‘10 Fawcett St.‘, city=‘Cambridge‘, state_province=‘MA‘, country=‘U.S.A.‘, website=‘http://www.oreilly.com/‘)
p1.save()

p2 = Publisher.objects.create(name="O‘Reilly", address=‘10 Fawcett St.‘, city=‘Cambridge‘, state_province=‘MA‘, country=‘U.S.A.‘, website=‘http://www.oreilly.com/‘)

 2. 查询对象

publisher_list = Publisher.objects.all()   #返回querySet，一个伪列表对象

publisher_list = Publisher.objects.filter(name=‘Jerry‘) #此处精确匹配name

publisher_list = Publisher.objects.filter(name__contains=‘Jerry‘) #此处模糊匹配name

publisher_list = Publisher.objects.filter(name__contains=‘Jerry‘).order_by(‘name‘) #按字母表正向排序

publisher_list = Publisher.objects.filter(name__contains=‘Jerry‘).order_by(‘-name‘) #按字母表逆向排序

publisher = Publisher.objects.get(name=‘Jerry‘)  #返回单个对象，此方法会抛出异常，Publisher.DoesNotExist、MultipleObjectsReturned

3. 更新对象

p1 = Publisher(name="O‘Reilly", address=‘10 Fawcett St.‘, city=‘Cambridge‘, state_province=‘MA‘, country=‘U.S.A.‘, website=‘http://www.oreilly.com/‘)
p1.save()

p1.name=‘update name‘

p1.save()   #此方法会更新所有字段，影响性能并且可能会引发竞态条件

Publisher.objects.filter(id=52).update(name=‘Apress Publishing‘)  #此方法只更新指定字段，可以有多个参数

4. 删除对象

p = Publisher.objects.get(name="O‘Reilly")
p.delete()
Publisher.objects.all()

Publisher.objects.all().delete()  #谨慎使用

django数据库模型

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