django数据库基本操作-增删改查（tip）-基本

补充:django外键保存

                #外键保存
                form_data = Form_Data()
                project, is_created = Project_Name.objects.get_or_create(name=select_text)
                form_data.project = project

1、插入数据

 Python代码
 >>> from books.models import Publisher
 >>> p1 = Publisher(name='Apress', address='2855 Telegraph Avenue',
 ...     city='Berkeley', state_province='CA', country='U.S.A.',
 ...     website='http://www.apress.com/')
 >>> p1.save()  

 >>> from books.models import Publisher
 >>> p1 = Publisher(name='Apress', address='2855 Telegraph Avenue',
 ...     city='Berkeley', state_province='CA', country='U.S.A.',
 ...     website='http://www.apress.com/')
 >>> p1.save()  

2、查询

 Python代码
 >>> Publisher.objects.all()
 [<Publisher: Apress>, <Publisher: O'Reilly>]  

 [python] view plain copy
 >>> Publisher.objects.all()
 [<Publisher: Apress>, <Publisher: O'Reilly>]  

获取单个对象：

 Python代码
 >>> Publisher.objects.get(name="Apress")
 <Publisher: Apress>  

 [python] view plain copy
 >>> Publisher.objects.get(name="Apress")
 <Publisher: Apress>  

如果结果是多个对象或者没有返回结果则会抛出异常

3、条件

筛选：

 Python代码
 >>> Publisher.objects.filter(name='Apress')
 [<Publisher: Apress>] 

 >>> Publisher.objects.filter(name='Apress')
 [<Publisher: Apress>]  

 Python代码
 >>> Publisher.objects.filter(name__contains="press")
 [<Publisher: Apress>]  

 [python] view plain copy
 >>> Publisher.objects.filter(name__contains="press")
 [<Publisher: Apress>] 

__contains部分会被Django翻译成LIKE语句

排序：

 Python代码
 >>> Publisher.objects.order_by("name")
 [<Publisher: Apress>, <Publisher: O'Reilly>

 python] view plain copy
 >>> Publisher.objects.order_by("name")
 [<Publisher: Apress>, <Publisher: O'Reilly>]  

相当于 order by name asc

 Python代码
 >>> Publisher.objects.order_by("-name")  

 [python] view plain copy
 >>> Publisher.objects.order_by("-name") 

加个负号相当于 order by name desc

限制返回数据：

 Python代码
 >>> Publisher.objects.order_by('name')[0]
 <Publisher: Apress>  

 [python] view plain copy
 >>> Publisher.objects.order_by('name')[0]
 <Publisher: Apress>

相当于 limit 1

 Python代码
 >>> Publisher.objects.order_by('name')[0:2]  

 [python] view plain copy
 >>> Publisher.objects.order_by('name')[0:2]  

相当于 OFFSET 0 LIMIT 2

4、更新

 Python代码
 >>> Publisher.objects.filter(id=52).update(name='Apress Publishing')  

 [python] view plain copy
 >>> Publisher.objects.filter(id=52).update(name='Apress Publishing')  

 Python代码
 >>> p = Publisher.objects.get(name='Apress') #先查询
 >>> p.name = 'Apress Publishing' #更新
 >>> p.save()  #保存  

 [python] view plain copy
 >>> p = Publisher.objects.get(name='Apress') #先查询
 >>> p.name = 'Apress Publishing' #更新
 >>> p.save()  #保存  

5、删除

 Python代码
 >>> p = Publisher.objects.get(name="O'Reilly")
 >>> p.delete()  

 [python] view plain copy
 >>> p = Publisher.objects.get(name="O'Reilly")
 >>> p.delete()  

 Python代码
 >>> Publisher.objects.filter(country='USA').delete() 

 [python] view plain copy
 >>> Publisher.objects.filter(country='USA').delete()