Django 操作 ORM 小笔记
报错内容：
You are trying to add a non-nullable field 'mobile' to user without a default; we can't do that (the database needs something to popula
te existing rows).
Please select a fix:
- Provide a one-off default now (will be set on all existing rows with a null value for this column)
- Quit, and let me add a default in models.py
Select an option:
models.py内容如下：
from django.db import models
from django.contrib.auth.models import AbstractUser
class User(AbstractUser):
mobile = models.CharField(max_length=11, unique=True, verbose_name='手机号')
class Meta:
db_table = 'users'
verbose_name = '用户'
verbose_name_plural = verbose_name
def __str__(self):
return self.username
这个模型类继承了AbstractUser类，这个类默认提供了很多属性，比如username、first_name、email等，但是没有mobile属性。
因此这里的mobile是我们自己加的。
当新加的mobile属性这样写时：
mobile = models.CharField(max_length=11, unique=True, verbose_name='手机号')
由于没有指定该字段的默认值，即没有指定这个字段是否可以为空，所以django会有这样的提示。
解决方案：
方案①
输入1，手动指定默认值为当前时间(timezone.now为带时区的当前时间，格式：2015-07-10 14:11:19.936835+00:00)，迁移就会继续。
$ python manage.py makemigrations
You are trying to add a non-nullable field 'mobile' to user without a default; we can't do that (the database needs something to popula
te existing rows).
Please select a fix:
1) Provide a one-off default now (will be set on all existing rows with a null value for this column)
2) Quit, and let me add a default in models.py
Select an option: 1
Please enter the default value now, as valid Python
The datetime and django.utils.timezone modules are available, so you can do e.g.
timezone.now
Type 'exit' to exit this prompt
>>> timezone.now
Migrations for 'user':
easybook/apps/user/migrations/0006_user_mobile.py
- Add field mobile to user
$ python manage.py migrate
方案②
输入2，退出当前对话，返回修改mobile属性的指定方式：
mobile = models.CharField(max_length=11, unique=True, null=True, verbose_name='手机号') # 增加null=True，即允许此字段为空
$ python manage.py makemigrations
Migrations for 'user':
easybook/apps/user/migrations/0008_user_mobile.py
- Add field mobile to user
$ python manage.py migrate