blocks|key|506817|text|您需要提供一个默认值：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|506818|new_field+=+models.CharField(max_length=140,+default='SOME+STRING')|code-block|syntax|javascript|506819|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

You need to provide a default value:

<pre><code>new_field = models.CharField(max_length=140, default='SOME STRING')
</code></pre>

blocks|key|731387|text|如果“网站”可以是空的，new_field也应该设置为空。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|731388|现在，如果您想在保存中添加逻辑，如果new_field为空以从“网站”获取值，则只需重写Model的保存函数，如下所示：|731389|class+UserProfile(models.Model):
++++user+=+models.OneToOneField(User)
++++website+=+models.URLField(blank=True,+default='DEFAULT+VALUE')
++++new_field+=+models.CharField(max_length=140,+blank=True,+default='DEFAULT+VALUE')

++++def+save(self,+*args,+**kwargs):
++++++++if+not+self.new_field:
++++++++++++#+Setting+the+value+of+new_field+with+website's+value
++++++++++++self.new_field+=+self.website

++++++++#+Saving+the+object+with+the+default+save()+function
++++++++super(UserProfile,+self).save(*args,+**kwargs)|code-block|syntax|javascript|731390|entityMap^0|C|9|0|I|9|18|5|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|R|8|@$9|S|A|T|B|C]|$9|U|A|V|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|W|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|X|8|@]|D|@]|E|$]]]|N|$]]

If "website" can be empty than <code>new_field</code> should also be set to be empty.

Now if you want to add logic on save where if <code>new_field</code> is empty to grab the value from "website" all you need to do is override the save function for your <code>Model</code> like this:

<pre><code>class UserProfile(models.Model):
 user = models.OneToOneField(User)
 website = models.URLField(blank=True, default='DEFAULT VALUE')
 new_field = models.CharField(max_length=140, blank=True, default='DEFAULT VALUE')

 def save(self, *args, **kwargs):
 if not self.new_field:
 # Setting the value of new_field with website's value
 self.new_field = self.website

 # Saving the object with the default save() function
 super(UserProfile, self).save(*args, **kwargs)
</code></pre>

blocks|key|731392|text|一个选项是声明‘new_field’的默认值：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|731393|new_field+=+models.CharField(max_length=140,+default='DEFAULT+VALUE')|code-block|syntax|javascript|731394|另一个选项是将'new_field‘声明为可空字段：|731395|new_field+=+models.CharField(max_length=140,+null=True)|731396|如果您决定接受'new_field‘作为一个空字段，您可能希望接受'no+input’作为'new_field‘的有效输入。然后还必须添加blank=True语句：|offset|length|style|CODE|731397|new_field+=+models.CharField(max_length=140,+blank=True,+null=True)|731398|即使使用null=True和/或blank=True，如果有必要，也可以添加默认值：|731399|new_field+=+models.CharField(max_length=140,+default='DEFAULT+VALUE',+blank=True,+null=True)|731400|entityMap^0|0|0|0|0|1X|A|0|0|4|9|G|A|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|Z|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|10|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|12|8|@$M|13|N|14|O|P]]|9|@]|A|$]]|$1|Q|3|R|5|D|7|15|8|@]|9|@]|A|$E|F]]|$1|S|3|T|5|6|7|16|8|@$M|17|N|18|O|P]|$M|19|N|1A|O|P]]|9|@]|A|$]]|$1|U|3|V|5|D|7|1B|8|@]|9|@]|A|$E|F]]|$1|W|3|-4|5|6|7|1C|8|@]|9|@]|A|$]]]|X|$]]

One option is to declare a default value for 'new_field':

<pre><code>new_field = models.CharField(max_length=140, default='DEFAULT VALUE')
</code></pre>

another option is to declare 'new_field' as a nullable field:

<pre><code>new_field = models.CharField(max_length=140, null=True)
</code></pre>

If you decide to accept 'new_field' as a nullable field you may want to accept 'no input' as valid input for 'new_field'. Then you have to add the <code>blank=True</code> statement as well:

<pre><code>new_field = models.CharField(max_length=140, blank=True, null=True)
</code></pre>

Even with <code>null=True</code> and/or <code>blank=True</code> you can add a default value if necessary:

<pre><code>new_field = models.CharField(max_length=140, default='DEFAULT VALUE', blank=True, null=True)
</code></pre>

blocks|key|504415|text|在new_file中添加布尔属性null。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|504416|new_field+=+models.CharField(max_length=140,+null=True)|code-block|syntax|javascript|504417|在运行./manage.py+syncdb以刷新DB之后。最后运行./manage.py+makemigrations和./manage.py+migrate|offset|length|style|CODE|504418|entityMap^0|0|0|3|I|X|Q|1O|J|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]|$I|T|J|U|K|L]|$I|V|J|W|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|X|8|@]|9|@]|A|$]]]|N|$]]

In new_file add the boolean property null.

<pre><code>new_field = models.CharField(max_length=140, null=True)
</code></pre>

after you run a <code>./manage.py syncdb</code> for refresh the DB. 
and finally you run <code>./manage.py makemigrations</code> 
and <code>./manage.py migrate</code>

blocks|key|506836|text|，如果您正处于早期开发周期，而不关心当前的数据库数据，您只需删除它，然后迁移即可。但是首先，您需要清理迁移dir并从表(django_migrations)中删除它的行。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|506837|rm++your_app/migrations/*+|code-block|syntax|javascript|506838|注意:不要删除迁移文件夹中的__+init+_+.py。|506839|rm+db.sqlite3
python+manage.py+makemigrations
python+manage.py+migrate|506840|如果您以前为Django的Admin应用程序创建了一个超级用户，那么您可能需要再次创建用户。|506841|entityMap^0|0|2D|0|0|0|S|0|0|0|1A|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|W|8|@$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|M|3|N|5|H|7|Z|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|10|8|@$9|11|A|12|B|C]]|D|@]|E|$]]|$1|Q|3|-4|5|6|7|13|8|@]|D|@]|E|$]]]|R|$]]

If you are in early development cycle and don't care about your current database data you can just remove it and then migrate. But first you need to clean migrations dir and remove its rows from table (django_migrations)
<pre><code>rm your_app/migrations/* 
</code></pre>
Note: Don't delete _ _ init _ _ .py in the migrations folder.
<pre><code>rm db.sqlite3
python manage.py makemigrations
python manage.py migrate
</code></pre>
If you previously created a superuser for Django's Admin web app then you might need to create the user again.

blocks|key|300638|text|表UserProfile中已经有数据库条目了吗？如果是这样的话，当您添加新列时，DB不知道将其设置为什么，因为它不能是NULL。因此，它会询问您希望将列new_fields中的这些字段设置为什么。为了解决这个问题，我不得不删除表中的所有行。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|BOLD|entityRanges|data|300639|(我知道这个问题在一段时间前就得到了回答，但我只是遇到了这个问题，这就是我的解决办法。希望它能帮助任何新认识到这个的人)|300640|entityMap^0|1|B|1N|4|24|A|33|2|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@$9|L|A|M|B|C]|$9|N|A|O|B|C]|$9|P|A|Q|B|C]|$9|R|A|S|B|D]]|E|@]|F|$]]|$1|G|3|H|5|6|7|T|8|@]|E|@]|F|$]]|$1|I|3|-4|5|6|7|U|8|@]|E|@]|F|$]]]|J|$]]

Do you already have database entries in the table <code>UserProfile</code>? If so, when you add new columns the DB doesn't know what to set it to because it can't be <code>NULL</code>. Therefore it asks you what you want to set those fields in the column <code>new_fields</code> to. I had to delete all the rows from this table to solve the problem.

(I know this was answered some time ago, but I just ran into this problem and this was my solution. Hopefully it will help anyone new that sees this)

blocks|key|504457|text|您可以使用这个页面中的Django的方法，https://docs.djangoproject.com/en/1.8/ref/models/fields/#default|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|504458|创建默认值并使用它|504459|def+contact_default():
+++return+{"email":+"to1@example.com"}

contact_info+=+JSONField("ContactInfo",+default=contact_default)|code-block|syntax|javascript|504460|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.djangoproject.com/en/1.8/ref/models/fields/#default^0|L|1S|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@$A|T|B|U|1|V]]|C|$]]|$1|D|3|E|5|6|7|W|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|X|8|@]|9|@]|C|$I|J]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]]]

You can use method from Django Doc from this page <a href="https://docs.djangoproject.com/en/1.8/ref/models/fields/#default" rel="nofollow">https://docs.djangoproject.com/en/1.8/ref/models/fields/#default</a>

Create default and use it

<pre><code>def contact_default():
 return {"email": "to1@example.com"}

contact_info = JSONField("ContactInfo", default=contact_default)
</code></pre>

blocks|key|731529|text|如果你处于开发周期的早期，你可以试试-|type|unstyled|depth|inlineStyleRanges|entityRanges|data|731530|删除/注释该模型及其所有用法。申请移民。这将删除该模型，然后再次添加该模型，运行迁移，然后添加一个干净的模型并添加新字段。|731531|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

If you are early into the development cycle you can try this - 

Remove/comment that model and all its usages. Apply migrations. That would delete that model and then add the model again, run migrations and you have a clean model with the new field added.

blocks|key|300727|text|Django实际上说的是：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|300728|Userprofile表中包含数据，其中可能存在为null的new_field值，但我不知道，因此您确定要将属性标记为非空属性，因为如果有空值，则可能会出现错误。
|blockquote|offset|length|style|CODE|300729|300730|如果您确信userprofile表中没有一个值是空的，则忽略警告。|300731|这种情况下的最佳实践是创建一个RunPython迁移，以处理选项2中所述的空值。|300732|2)暂时忽略，让我自己处理现有行(例如，在以前的数据迁移中添加了一个RunPython或RunSQL操作来处理空值)
|300733|300734|在RunPython迁移中，您必须找到所有带有空new_field值的UserProfile实例，并在其中放置一个正确的值(或者按Django要求在模型中设置的默认值)。你会得到这样的东西：|300735|#+please+keep+in+mind+that+new_value+can+be+an+empty+string.+You+decide+whether+it+is+a+correct+value.
for+profile+in+UserProfile.objects.filter(new_value__isnull=True).iterator():
++++profile.new_value+=+calculate_value(profile)
++++profile.save()+#+better+to+use+batch+save|code-block|syntax|javascript|300736|玩得开心!|300737|entityMap^0|0|U|9|0|0|5|B|0|0|0|0|O|9|Z|B|0|0|0^^$0|@$1|2|3|4|5|6|7|11|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|12|8|@$E|13|F|14|G|H]]|9|@]|A|$]]|$1|I|3|-4|5|6|7|15|8|@]|9|@]|A|$]]|$1|J|3|K|5|6|7|16|8|@$E|17|F|18|G|H]]|9|@]|A|$]]|$1|L|3|M|5|6|7|19|8|@]|9|@]|A|$]]|$1|N|3|O|5|D|7|1A|8|@]|9|@]|A|$]]|$1|P|3|-4|5|6|7|1B|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|1C|8|@$E|1D|F|1E|G|H]|$E|1F|F|1G|G|H]]|9|@]|A|$]]|$1|S|3|T|5|U|7|1H|8|@]|9|@]|A|$V|W]]|$1|X|3|Y|5|6|7|1I|8|@]|9|@]|A|$]]|$1|Z|3|-4|5|6|7|1J|8|@]|9|@]|A|$]]]|10|$]]

What Django actually says is:

<blockquote>
 Userprofile table has data in it and there might be <code>new_field</code> values
 which are null, but I do not know, so are you sure you want to mark
 property as non nullable, because if you do you might get an error if
 there are values with NULL
</blockquote>

If you are sure that none of values in the <code>userprofile</code> table are NULL - fell free and ignore the warning. 

The best practice in such cases would be to create a RunPython migration to handle empty values as it states in option 2

<blockquote>
 2) Ignore for now, and let me handle existing rows with NULL myself (e.g. because you added a RunPython or RunSQL operation to handle NULL values in a previous data migration)
</blockquote>

In RunPython migration you have to find all <code>UserProfile</code> instances with empty <code>new_field</code> value and put a correct value there (or a default value as Django asks you to set in the model).
You will get something like this:

<pre><code># please keep in mind that new_value can be an empty string. You decide whether it is a correct value.
for profile in UserProfile.objects.filter(new_value__isnull=True).iterator():
 profile.new_value = calculate_value(profile)
 profile.save() # better to use batch save
</code></pre>

Have fun!

blocks|key|506889|text|老实说，我发现解决这个问题的最好方法就是创建另一个模型，其中包含您所需的所有字段，并且命名略有不同。进行迁移。删除未使用的模型并再次运行迁移。瞧。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|506890|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

I honestly fount the best way to get around this was to just create another model with all the fields that you require and named slightly different. Run migrations. Delete unused model and run migrations again. Voila.

blocks|key|300807|text|如果SSH给了你2个选项，选择数字1，然后加上"None“。就在此刻that...for。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|300808|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

If the SSH it gives you 2 options, choose number 1, and put "None". Just that...for the moment.

blocks|key|504517|text|不能添加对表中已经有数据的引用。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|504518|更改：|504519|user+=+models.OneToOneField(User)|code-block|syntax|javascript|504520|至：|504521|user+=+models.OneToOneField(User,+default+=+"")|504522|做：|504523|python+manage.py+makemigrations
python+manage.py+migrate|504524|再次改变：|504525|user+=+models.OneToOneField(User)|504526|再次移徙：|504527|python+manage.py+makemigrations
python+manage.py+migrate|504528|entityMap^0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|11|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|12|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|13|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|14|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|15|8|@]|9|@]|A|$]]|$1|O|3|P|5|F|7|16|8|@]|9|@]|A|$G|H]]|$1|Q|3|R|5|6|7|17|8|@]|9|@]|A|$]]|$1|S|3|T|5|F|7|18|8|@]|9|@]|A|$G|H]]|$1|U|3|V|5|6|7|19|8|@]|9|@]|A|$]]|$1|W|3|X|5|F|7|1A|8|@]|9|@]|A|$G|H]]|$1|Y|3|-4|5|6|7|1B|8|@]|9|@]|A|$]]]|Z|$]]

You can't add reference to table that have already data inside. 
Change:

<pre><code>user = models.OneToOneField(User)
</code></pre>

to:

<pre><code>user = models.OneToOneField(User, default = "")
</code></pre>

do:

<pre><code>python manage.py makemigrations
python manage.py migrate
</code></pre>

change again:

<pre><code>user = models.OneToOneField(User)
</code></pre>

do migration again:

<pre><code>python manage.py makemigrations
python manage.py migrate
</code></pre>

blocks|key|731661|text|如果您对截断有关模型的表很满意，则可以在提示符中指定一次性默认值None。迁移将有多余的default=None，而您的代码没有默认设置。它可以很好地应用，因为表中不再有数据需要默认设置。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|731662|entityMap^0|W|4|18|C|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|M|8|@]|D|@]|E|$]]]|G|$]]

If you are fine with truncating the table of the model in question, you can specify a one-off default value of <code>None</code> in the prompt. The migration will have superfluous <code>default=None</code> while your code has no default. It can be applied just fine because there's no data in the table anymore which would require a default.

blocks|key|731671|text|在models.py中|type|unstyled|depth|inlineStyleRanges|entityRanges|data|731672|class+UserProfile(models.Model):+++++user+=+models.OneToOneField(User)+++++website+=+models.URLField(blank=True)+++++new_field+=+models.CharField(max_length=140,+default="some_value")|offset|length|style|CODE|731673|您需要添加一些值作为默认值。|731674|entityMap^0|0|0|53|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|M|8|@$D|N|E|O|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|P|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|K|$]]

In models.py

<code>class UserProfile(models.Model):
 user = models.OneToOneField(User)
 website = models.URLField(blank=True)
 new_field = models.CharField(max_length=140, default="some_value")</code> 

You need to add some values as default.

blocks|key|504570|text|我在我的开发周期早期，所以这可能并不适用于每个人(但我不明白为什么它不能)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|504571|我将blank=True,+null=True添加到我获得错误的列中。然后运行python+manage.py+makemigrations命令。|offset|length|style|CODE|504572|在运行此命令之后(在运行python+manage.py+migrate之前)，我将blank=True,+null=True从所有列中移除。然后我又运行了python+manage.py+makemigrations。我得到了一个选项，可以自己更改列，我选择了这些列。|504573|然后我运行了python+manage.py+migrate，一切都进行得很好！|504574|entityMap^0|0|2|L|13|V|0|C|O|16|L|26|V|0|6|O|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@$D|P|E|Q|F|G]|$D|R|E|S|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|T|8|@$D|U|E|V|F|G]|$D|W|E|X|F|G]|$D|Y|E|Z|F|G]]|9|@]|A|$]]|$1|J|3|K|5|6|7|10|8|@$D|11|E|12|F|G]]|9|@]|A|$]]|$1|L|3|-4|5|6|7|13|8|@]|9|@]|A|$]]]|M|$]]

I was early in my development cycle, so this may not work for everyone (but I don't see why it wouldn't). 

I added <code>blank=True, null=True</code> to the columns where I was getting the error. Then I ran the <code>python manage.py makemigrations</code> command. 

Immediately after running this command (and before running <code>python manage.py migrate</code>), I removed the <code>blank=True, null=True</code> from all the columns. Then I ran <code>python manage.py makemigrations</code> again. I was given an option to just change the columns myself, which I selected. 

Then I ran <code>python manage.py migrate</code> and everything worked well!

blocks|key|300917|text|如果有人正在设置ForeignKey，您可以只允许空字段而不设置默认值：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|300918|new_field+=+models.ForeignKey(model,+null=True)|code-block|syntax|javascript|300919|如果数据库中已经存储了数据，还可以设置默认值：|300920|new_field+=+models.ForeignKey(model,+default=<existing+model+id+here>)|300921|entityMap^0|8|A|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|U|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|W|8|@]|D|@]|E|$]]]|P|$]]

In case anyone is setting a <code>ForeignKey</code>, you can just allow nullable fields without setting a default:

<pre><code>new_field = models.ForeignKey(model, null=True)
</code></pre>

If you already have data stored within the database, you can also set a default value:

<pre><code>new_field = models.ForeignKey(model, default=&lt;existing model id here&gt;)
</code></pre>

blocks|key|300958|text|基本上，我解决了这个问题，将null=True添加到添加的模型中。例如：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|300959|我试图在现有的数据库模块中添加phone_number。|300960|phone_number+=+models.CharField(max_length=10)|code-block|syntax|javascript|300961|我以前收到过这样的错误：|300962|您正在尝试在没有默认情况下向客户添加一个非空字段“phone_number”；我们不能这样做(数据库需要一些东西来填充现有行)。请选择一个修补程序：
|blockquote|300963|300964|立即提供一次性默认值(将在现有的所有行上设置此列的空值)|ordered-list-item|300965|退出，让我在models.py中添加一个默认值|300966|300967|300968|放完后|300969|phone_number+=+models.CharField(max_length=10,+null=True)

python+manage.py+makemigrations
Migrations+for+'collegekhajagharapp':
++collegekhajagharapp\migrations\0002_customer_phone_number.py
++++-+Add+field+phone_number+to+customer|300970|entityMap^0|E|9|0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|15|8|@$9|16|A|17|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|18|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|19|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|1A|8|@]|D|@]|E|$]]|$1|O|3|P|5|Q|7|1B|8|@]|D|@]|E|$]]|$1|R|3|-4|5|6|7|1C|8|@]|D|@]|E|$]]|$1|S|3|T|5|U|7|1D|8|@]|D|@]|E|$]]|$1|V|3|W|5|U|7|1E|8|@]|D|@]|E|$]]|$1|X|3|-4|5|6|7|1F|8|@]|D|@]|E|$]]|$1|Y|3|-4|5|6|7|1G|8|@]|D|@]|E|$]]|$1|Z|3|10|5|6|7|1H|8|@]|D|@]|E|$]]|$1|11|3|12|5|J|7|1I|8|@]|D|@]|E|$K|L]]|$1|13|3|-4|5|6|7|1J|8|@]|D|@]|E|$]]]|14|$]]

Basically I solved this Issue putting <code>null=True</code> in added model.
For example:
I was trying to add phone_number in the existing database module.
<pre><code>phone_number = models.CharField(max_length=10)
</code></pre>
I previously got this error:
<blockquote>
You are trying to add a non-nullable field 'phone_number' to customer
without a default; we can't do that (the database needs something to
populate existing rows). Please select a fix:
<ol>
<li>Provide a one-off
default now (will be set on all existing rows with a null value for
this column)</li>
<li>Quit, and let me add a default in models.py</li>
</ol>
</blockquote>
After putting
<pre><code>phone_number = models.CharField(max_length=10, null=True)

python manage.py makemigrations
Migrations for 'collegekhajagharapp':
 collegekhajagharapp\migrations\0002_customer_phone_number.py
 - Add field phone_number to customer
</code></pre>

blocks|key|731767|text|如果您的表是新的，并且您不关心这些数据，请执行以下步骤：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|731768|Delete+FROM+public.django_migrations+where+app=<your_app_name>|ordered-list-item|offset|length|style|CODE|731769|Delete+all+migrations+file+from+your+project|731770|DROP+table+<your_table_name>|731771|python+manage.py+makemigrations|731772|python+manage.py+migrate|731773|731774|731775|如果您关心数据，那么在您的字段中添加一个默认值|731776|new_field+=+models.CharField(max_length=140,+default='your_default_value')|code-block|syntax|javascript|731777|entityMap^0|0|0|1Q|0|0|18|0|0|S|0|0|V|0|0|O|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|11|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|12|8|@$E|13|F|14|G|H]]|9|@]|A|$]]|$1|I|3|J|5|D|7|15|8|@$E|16|F|17|G|H]]|9|@]|A|$]]|$1|K|3|L|5|D|7|18|8|@$E|19|F|1A|G|H]]|9|@]|A|$]]|$1|M|3|N|5|D|7|1B|8|@$E|1C|F|1D|G|H]]|9|@]|A|$]]|$1|O|3|P|5|D|7|1E|8|@$E|1F|F|1G|G|H]]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|1H|8|@]|9|@]|A|$]]|$1|R|3|-4|5|6|7|1I|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|1J|8|@]|9|@]|A|$]]|$1|U|3|V|5|W|7|1K|8|@]|9|@]|A|$X|Y]]|$1|Z|3|-4|5|6|7|1L|8|@]|9|@]|A|$]]]|10|$]]

If your table is new and you dont care about the data follow below steps:
<ol>
<li><code>Delete FROM public.django_migrations where app=&lt;your_app_name&gt;</code></li>
<li><code>Delete all migrations file from your project</code></li>
<li><code>DROP table &lt;your_table_name&gt;</code></li>
<li><code>python manage.py makemigrations</code></li>
<li><code>python manage.py migrate</code></li>
</ol>
If you care about data, then add a default to your field
<pre><code>new_field = models.CharField(max_length=140, default='your_default_value')
</code></pre>

blocks|key|506992|text|这里有一个解决方案，不需要做出妥协，例如删除所有现有的数据/迁移(yikes)，需要两个单独的迁移，或者设置一个不必要的默认设置。采取以下步骤：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|506993|使用null=False将新字段添加到模型中|ordered-list-item|offset|length|style|CODE|506994|python+manage.py+makemigrations+<app_name>+--name+<migration_name>|506995|将新字段更改为null=True|506996|python+manage.py+makemigrations+<app_name>。在这个步骤中，您将看到一个您可能从未见过的选项！您需要选项2：“暂时忽略，让我自己处理带有NULL的现有行(例如，在以前的数据迁移中添加了RunPython或RunSQL操作来处理空值)。”|506997|506998|506999|📷|atomic|507000|​|507001|将migrations.AlterField操作从第二次迁移移到第一次迁移，并添加手动迁移来处理NULL值(如果不执行此步骤，您将得到与前面一样的完整性错误)，如下所示：|507002|507003|507004|def+initial_display_names(apps,+schema):
++++Player+=+apps.get_model('my_app',+'Player')
++++Player.objects.all().update(display_name='Cool+Name')

def+reversal(*args):
++++"""Reversal+is+NOOP+since+display_name+is+simply+dropped+during+reverse"""


class+Migration(migrations.Migration):

++++dependencies+=+[
++++++++('my_app',+'0049_foo'),
++++]

++++operations+=+[
++++++++migrations.AddField(
++++++++++++model_name='player',
++++++++++++name='display_name',
++++++++++++field=models.CharField(help_text='name+as+shown+in+the+UI',+max_length=256,+null=True),
++++++++),
++++++++migrations.RunPython(initial_display_names,+reversal),
++++++++migrations.AlterField(
++++++++++++model_name='player',
++++++++++++name='display_name',
++++++++++++field=models.CharField(help_text='name+as+shown+in+the+UI',+max_length=256),
++++++++),
++++]|code-block|syntax|javascript|507005|删除您所做的第二次迁移。|507006|python+manage.py+migrate+<app_name>|507007|507008|507009|entityMap|0|IMAGE|mutability|IMMUTABLE|imageUrl|https://developer.qcloudimg.com/http-save/yehe-900000/8116e6e845bd4039a872e9c424b19657.png|imageAlt^0|0|2|A|0|0|1U|0|7|9|0|0|16|0|0|0|0|1|0|0|0|1|L|1C|4|0|0|0|0|0|0|Z|0|0|0^^$0|@$1|2|3|4|5|6|7|1J|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|1K|8|@$E|1L|F|1M|G|H]]|9|@]|A|$]]|$1|I|3|J|5|D|7|1N|8|@$E|1O|F|1P|G|H]]|9|@]|A|$]]|$1|K|3|L|5|D|7|1Q|8|@$E|1R|F|1S|G|H]]|9|@]|A|$]]|$1|M|3|N|5|D|7|1T|8|@$E|1U|F|1V|G|H]]|9|@]|A|$]]|$1|O|3|-4|5|6|7|1W|8|@]|9|@]|A|$]]|$1|P|3|-4|5|6|7|1X|8|@]|9|@]|A|$]]|$1|Q|3|R|5|S|7|1Y|8|@]|9|@$E|1Z|F|20|1|21]]|A|$]]|$1|T|3|U|5|6|7|22|8|@]|9|@]|A|$]]|$1|V|3|W|5|D|7|23|8|@$E|24|F|25|G|H]|$E|26|F|27|G|H]]|9|@]|A|$]]|$1|X|3|-4|5|6|7|28|8|@]|9|@]|A|$]]|$1|Y|3|-4|5|6|7|29|8|@]|9|@]|A|$]]|$1|Z|3|10|5|11|7|2A|8|@]|9|@]|A|$12|13]]|$1|14|3|15|5|D|7|2B|8|@]|9|@]|A|$]]|$1|16|3|17|5|D|7|2C|8|@$E|2D|F|2E|G|H]]|9|@]|A|$]]|$1|18|3|-4|5|6|7|2F|8|@]|9|@]|A|$]]|$1|19|3|-4|5|6|7|2G|8|@]|9|@]|A|$]]|$1|1A|3|-4|5|6|7|2H|8|@]|9|@]|A|$]]]|1B|$1C|$5|1D|1E|1F|A|$1G|1H|1I|-4]]]]

Here is a workaround without having to make compromises such as dropping all existing data/migrations (yikes), requiring two separate migrations, or setting an unwanted default. Take these steps:
<ol>
<li>Add the new field to your model with <code>null=False</code></li>
<li><code>python manage.py makemigrations &lt;app_name&gt; --name &lt;migration_name&gt;</code></li>
<li>Change the new field to <code>null=True</code></li>
<li><code>python manage.py makemigrations &lt;app_name&gt;</code>. In this step, you'll see an option you may never have seen before! You want option 2: &quot;Ignore for now, and let me handle existing rows with NULL myself (e.g. because you added a RunPython or RunSQL operation to handle NULL values in a previous data migration)&quot; <a href="https://i.stack.imgur.com/7R1QV.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/7R1QV.png" alt="enter image description here" /></a></li>
<li>Move the <code>migrations.AlterField</code> operation from the second migration into the first one, and add a manual migration to take care of the <code>NULL</code> values (if you don't take this step you'll get integrity errors like before), like so:</li>
</ol>
<pre class="lang-py prettyprint-override"><code>def initial_display_names(apps, schema):
 Player = apps.get_model('my_app', 'Player')
 Player.objects.all().update(display_name='Cool Name')

def reversal(*args):
 &quot;&quot;&quot;Reversal is NOOP since display_name is simply dropped during reverse&quot;&quot;&quot;


class Migration(migrations.Migration):

 dependencies = [
 ('my_app', '0049_foo'),
 ]

 operations = [
 migrations.AddField(
 model_name='player',
 name='display_name',
 field=models.CharField(help_text='name as shown in the UI', max_length=256, null=True),
 ),
 migrations.RunPython(initial_display_names, reversal),
 migrations.AlterField(
 model_name='player',
 name='display_name',
 field=models.CharField(help_text='name as shown in the UI', max_length=256),
 ),
 ]
</code></pre>
<ol start="6">
<li>Remove the second migration you made.</li>
<li><code>python manage.py migrate &lt;app_name&gt;</code></li>
</ol>

blocks|key|504632|text|删除模型=>生成模型=>迁移模型=>返回模型=>生成模型=>迁移模型|type|unstyled|depth|inlineStyleRanges|entityRanges|data|504633|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Delete Model =&gt; Makemigrations Models =&gt; Migrate Models =&gt; Return Back the models =&gt; Makemigrations Models =&gt; Migrate Models

I know that from Django 1.7 I don't need to use South or any other migration system, so I am just using simple command <code>python manage.py makemigrations</code>

However, all I get is this error: 

<pre><code>You are trying to add a non-nullable field 'new_field' to userprofile without a default;
we can't do that (the database needs something to populate existing rows).
</code></pre>

Here is models.py:

<pre><code>class UserProfile(models.Model):
 user = models.OneToOneField(User)
 website = models.URLField(blank=True)
 new_field = models.CharField(max_length=140)
</code></pre>

What are options?

You are trying to add a non-nullable field 'new_field' to userprofile without a default

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我知道从Django 1.7，我不需要使用南方或任何其他迁移系统，所以我只是使用简单的命令python manage.py makemigrations然而，我得到的只是这个错误：You are trying to add a non-nullable field 'new_field' to userprofile ...

问您正在尝试将非空字段“new_field”添加到用户配置文件中，而没有默认设置。
EN

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问您正在尝试将非空字段“new_field”添加到用户配置文件中，而没有默认设置。EN