从Django模型创建数据库视图 [英] Create database view from django model

问题描述

我将sql视图作为一个虚拟表来学习，以简化SQL操作，例如

  MySQL [distributor]>创建视图CustomerEMailList AS 
->选择cust_id，cust_name，cust_email 
->来自客户
-> cust_email不为空； 
查询正常，受影响的0行（0.026秒）
 
 MySQL [distributor]>从客户电子邮件列表中选择*； 
 + ------------ + --------------- + ---------------- ------- + 
 | cust_id | cust_name | cust_email | 
 + ------------ + --------------- + ---------------- ------- + 
 | 1000000001 |乡村玩具| [e-mail] | 
 | 1000000003 | Fun4All | [e-mail] | 
 | 1000000004 | Fun4All | [e-mail] | 
 | 1000000005 |玩具商店| [e-mail] | 
 | 1000000006 |玩具乐园| [e-mail] | 
 + ------------ + --------------- + ---------------- ------- + 
集合中的5行（0.014秒）
  

何时我随后查看了Django文档，没有创建虚拟模型表的功能，可以简化数据操作。

我应该忘记虚拟表视图在使用Django ORM时？

解决方案

Django就我所知，目前还没有内置的视图支持。 / p>

但是您可以使用> django-database-view 软件包。

安装软件包后（例如使用pip）：

  pip安装django-database-view 
  

此外，必须在 dbview 应用中注册 settings.py 文件：

 ＃settings.py 
 
 INSTALLED_APPS =（
＃... 
'dbview'，
＃... 
）
  

现在您可以构建视图了，这看起来与 的构建有点相似一个模型，除了需要实现 view（..）函数，该函数指定视图后的查询。类似于以下内容：

 从django.db导入模型
从dbview导入DbView 
 
 class CustomerEMailList（DbView）：
 cust = models.OneToOneField（Customer，primary_key = True）
 cust_name = models.CharField（）
 cust_email = models.CharField（）
 
 @classmethod 
 def view（klass）：
 qs =（Customers.objects.filter（cust_email__isnull = False）
 .values（'cust_id'，'cust_name'，'cust_email'） ）
 return str（qs.query）
  

现在我们可以进行迁移了：

  ./ manage.py makemigrations 
  

现在在迁移中，我们需要进行更改：对 migrations.CreateModel 的调用与构造的视图相关的strong>应该更改为 dbview 的 CreateView code>模块。看起来像这样：

 从django.db导入迁移
从dbview导入CreateView 
 
类Migration（migrations.Migration）：
 
依赖关系= [] 
 
操作= [
 CreateView（
 name ='CustomerEMailList'，
 fields = [
＃... 
]，
），
] 
  




I learned sql "view" as a virtual table to facilitate the SQL operations, like

MySQL [distributor]> CREATE VIEW CustomerEMailList AS
    -> SELECT cust_id, cust_name, cust_email
    -> FROM Customers
    -> WHERE cust_email IS NOT NULL;
Query OK, 0 rows affected (0.026 sec)

MySQL [distributor]> select * from customeremaillist;
+------------+---------------+-----------------------+
| cust_id    | cust_name     | cust_email            |
+------------+---------------+-----------------------+
| 1000000001 | Village Toys  | [e-mail] |
| 1000000003 | Fun4All       | [e-mail]    |
| 1000000004 | Fun4All       | [e-mail] |
| 1000000005 | The Toy Store | [e-mail]   |
| 1000000006 | toy land      | [e-mail]       |
+------------+---------------+-----------------------+
5 rows in set (0.014 sec)

When I checked the Django documentation subsequently, there are no such functionality to create a virtual "model table" which could simplify the data manipulation.

Should I forget the virtual table "view" when using Django ORM?

解决方案

Django has - as far as I know at the moment - no builtin support for views.

But you can construct such views, by using the django-database-view package.

After installing the package (for example with pip):

 pip install django-database-view

Furthermore the dbview app has to be registered in the settings.py file:

# settings.py

INSTALLED_APPS = (
    # ...
    'dbview',
    # ...
)

Now you can construct a view, this looks a bit similar to the construction of a model, except that you need to implement a view(..) function that specifies the query behind the view. Something similar to:

from django.db import models
from dbview import DbView

class CustomerEMailList(DbView):
    cust = models.OneToOneField(Customer, primary_key=True)
    cust_name = models.CharField()
    cust_email = models.CharField()

    @classmethod
    def view(klass):
        qs = (Customers.objects.filter(cust_email__isnull=False)
                               .values('cust_id', 'cust_name', 'cust_email'))
        return str(qs.query)

Now we can make a migrations:

./manage.py makemigrations

Now in the migration, we need to make a change: the calls to migrations.CreateModel that are related to the constructed view(s), should be changed to the CreateView of the dbview module. Something that looks like:

from django.db import migrations
from dbview import CreateView

class Migration(migrations.Migration):

    dependencies = []

    operations = [
        CreateView(
            name='CustomerEMailList',
            fields=[
                # ...
            ],
        ),
    ]

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