在django中缺少所需的Charfield保存为空字符串，不会引发错误 [英] missing required Charfield in django is saved as empty string and do not raise an error

问题描述

如果我尝试在Django 1.10中保存不完整的模型实例，我会期望Django引发错误。这似乎不是这样的。

If I try to save incomplete model instance in Django 1.10, I would expect Django to raise an error. It does not seem to be the case.

models.py：

models.py:

from django.db import models

class Essai(models.Model):
    ch1 = models.CharField(max_length=100, blank=False)
    ch2 = models.CharField(max_length=100, blank=False)

所以我有两个字段不允许为空Django在MySQL表创建时应用默认行为 NOT NULL 限制。我希望Django在存储之前未设置其中一个字段时发生错误。

So I have two fields not allowed to be empty (default behavior, NOT NULL restriction is applied by Django at MySQL table creation). I expect Django to rase an error if one of the fields is not set before storing.

但是，当我创建一个不完整的实例时，数据被存储很好： / p>

However, when I create an incomplete instance, the data is stored just fine:

>>> from test.models import Essai
>>> bouh = Essai()
>>> bouh.ch1 = "some content for ch1"
>>> bouh.save()
>>> bouh.id
9
>>> bouh.ch1
'some content for ch1'
>>> bouh.ch2
''
>>> 

我会期望Django引发错误。如果我强制 ch2 到无，则会引发错误：

I would have expected Django to raise an error. If I force ch2 to None, however, it raises an error:

>>> bouh = Essai()
>>> bouh.ch1 = "some content for ch1"
>>> bouh.ch2 = None
>>> bouh.save()
Traceback (most recent call last):
  (...)
    return Database.Cursor.execute(self, query, params)
django.db.utils.IntegrityError: NOT NULL constraint failed: test_essai.ch2
>>> bouh.id
>>> bouh.ch1
'some content for ch1'
>>> bouh.ch2
>>>

这是正常的行为吗？我错过了什么？为什么Django在这种简单的情况下不会将错误提升为默认行为？

Is this normal behavior? Did I miss something? Why is Django not raising an error as default behavior in this simple case?

感谢您的光！

编辑

我收到了一些回复，指出SQL空字符串 不等于NULL，如 Django中所述模型空白= False不起作用？
但是，如果我们看到ModelForm行为，django文档中似乎有一个不一致。

I got a few replies pointing out the fact that in SQL empty string "" is not equivalent to NULL, as stated in Django model blank=False does not work? However, if we look at ModelForm behavior, there seem to be a inconsistency in django doc.

见问题
跟进：在django中缺少所需的Charfield Modelform保存为空字符串，不会引发错误

推荐答案

看起来像你对于 [blank] [1] 代表

注意事项有轻微误解这不同于null。 null纯粹是
数据库相关，而空白与验证相关。如果一个字段有
blank = True，表单验证将允许输入一个空值。如果
字段为空= False，那么该字段将被要求。

Note that this is different than null. null is purely database-related, whereas blank is validation-related. If a field has blank=True, form validation will allow entry of an empty value. If a field has blank=False, the field will be required.

还有

避免在基于字符串的字段（如CharField和
TextField）上使用null，因为空字符串值将始终存储为空的
字符串，而不是空值。如果基于字符串的字段为null = True，那么
意味着它有两个可能的no data值：NULL和空的
字符串。在大多数情况下，对于
没有数据有两个可能的值是多余的;Django约定是使用空字符串，而不是NULL。

Avoid using null on string-based fields such as CharField and TextField because empty string values will always be stored as empty strings, not as NULL. If a string-based field has null=True, that means it has two possible values for "no data": NULL, and the empty string. In most cases, it’s redundant to have two possible values for "no data;" the Django convention is to use the empty string, not NULL.

所以在你的情况下，blank = false并不意味着django将拒绝为 ch1 或 ch2 。但是如果您使用ModelForm，它将拒绝让该字段留空。

Thus in your case, blank=false does not mean django will refuse to write an empty string for ch1 or ch2. but it will refuse to let you leave that field blank if you use a ModelForm with it.

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