更改模型中的 Django 数据类型而不删除表

发布于 2024-10-25 18:19:15 字数 623 浏览 3 评论 0原文

我创建了一个 Django 应用程序。现在我想更改模型中 1 个数据库字段的字段类型。由于数据库中已有一些具有当前类型的记录，我猜想通过简单地在 models.py 中更改它来更改类型是不可能的。通过谷歌搜索，我了解到可以通过 sql 控制台更改它，而无需删除表即可更改它。但作为 Django 新手，我无法做到这一点。有人可以帮我做到这一点吗？这是我的 models.py

class EmployeeDetails(models.Model):
    userName = models.CharField(max_length=200)
    designation = models.CharField(max_length=200)
    employeeID = models.IntegerField()
    contactNumber = models.CharField(max_length=200)
    project = models.CharField(max_length=200)
    dateOfJoin=models.TextField()

现在我想更改 dateOfJoin = models.DateField()。如何使用 sql 控制台命令将 TextField 更改为 DateField 而不删除表？

原文

I have created a Django application. Now i wanted to change the field type for 1 of my db field in models. Since there are some records already in the database with the present type, i guess its not possible to change the type by simply changing it in models.py. By googling i came to know that it can be changed without dropping the tables by changing it through sql console. But being a Django newbie i am not able to do this. Can somebody help me to do this? This is my models.py

class EmployeeDetails(models.Model):
    userName = models.CharField(max_length=200)
    designation = models.CharField(max_length=200)
    employeeID = models.IntegerField()
    contactNumber = models.CharField(max_length=200)
    project = models.CharField(max_length=200)
    dateOfJoin=models.TextField()

Now i want to change the dateOfJoin = models.DateField(). How can i change the TextFieild to DateField without droping the table by using sql console commands?

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深海少女心 2024-11-01 18:19:16

您需要的应用程序是South
以下是步骤（有关更多详细信息，请参阅文档）：

./manage.py convert_to_south yourapp

这将创建一个迁移文件夹并伪造第一次迁移

然后在 models.py 中添加一个 new_dateOfJoin DateField ：

./manage.py migrate yourapp

这将立即创建并应用迁移（名为 0002_...）以在数据库中添加此字段

创建一个 datamigration 0003 文件，您只需将文本值转换为日期并将其保存在新字段中
然后应用此迁移：

./manage.py migrate yourapp

修改您的 models.py 文件以注释掉旧的日期字段并再次迁移（这将创建 0004_.... 迁移文件）

最后一步是重命名 db 字段，这样您就不必修改您现有的代码：

./manage.py schemamigration yourapp rename_dateofjoin --empty

这将创建一个名为 0005_rename_dateofjoin
的空架构迁移文件
手动修改此 0005 文件，如此处所述，但是使用 db.rename_column('app_foo', 'name', 'full_name') 就像这个其他示例。

删除整个表而不是这 5 个步骤可能会更容易，但如果您有应用程序的多个实例（例如工作的生产服务器和开发机器），您需要这种工具。
随着对南方有了更好的了解，人们也可以在不到 5 个步骤内完成此操作，但由于迁移有时很难撤消或重现，所以我更喜欢有不同的步骤......

The app you need is South
Here are the steps (refer to the doc for more details) :

./manage.py convert_to_south yourapp

this will create a migration folder and fake a first migration

Then add a new_dateOfJoin DateField in your models.py :

./manage.py migrate yourapp

this will create and apply immediatly a migration (named 0002_...) to add this field in the db

Create a datamigration 0003 file where you will just cast your text value to date and save it in your new field
Then apply this migration :

./manage.py migrate yourapp

Modify your models.py file to comment out the old datefield and migrate again (this will create the 0004_.... migration file)

The last step is to rename the db field so you don't have to modify your existing code:

./manage.py schemamigration yourapp rename_dateofjoin --empty

This will create an empty schema migration file named 0005_rename_dateofjoin
Manually modify this 0005 file like explained here , but use db.rename_column('app_foo', 'name', 'full_name') like in this other example.

Dropping your whole table instead of these 5 steps can be easier, but if you have multiple instance of the app (like a working production server and a develpement machine) you need this kind of tools.
With better understanding of South, one could also do this in less than 5 steps, but as migrations can be tricky to undone or reproduce sometimes, I prefer to have distinct steps...

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