这里，是null=True和blank=True的主要区别:

null和blank的默认值都是False。这两个值都在字段级工作，即，我们是否想要保持字段为空或空白。

null=True将字段的值设置为null，即没有数据。它基本上是为数据库列的值。

date = models.DateTimeField(null=True)

blank=True确定表单中是否需要该字段。这包括管理表单和您自己的自定义表单。

title = models.CharField(blank=True) // title可以为空。 在数据库中(“”)将被存储。 null=True blank=True这意味着该字段在所有情况下都是可选的。

epic = models.ForeignKey(null=True, blank=True)
// The exception is CharFields() and TextFields(), which in Django are never saved as NULL. Blank values a

如果设置null=True，它将允许将数据库列的值设置为null。如果你只设置blank=True, django会为这个列设置默认的新值为""。

有一点，null=True将是必要的，即使在CharField或TextField，这是当数据库有唯一的标志设置列。在这种情况下，你需要使用这个:

a_unique_string = models.CharField(blank=True, null=True, unique=True)

最好跳过null=True的非唯一CharField或TextField。否则，一些字段将被设置为NULL，而另一些字段将被设置为“”，并且您必须每次检查字段值是否为NULL。

当我们在Django管理中保存任何东西时，会发生两步验证，在Django级别和数据库级别。我们不能在数字字段中保存文本。

数据库的数据类型是NULL，什么都不是。当Django在数据库中创建列时，它指定它们不能为空。如果你试图保存NULL，你会得到数据库错误。

同样在Django- admin级别，默认情况下所有字段都是必须的，你不能保存空白字段，Django会给你一个错误。

所以，如果你想保存空白字段，你需要在Django和数据库级别上允许它。 blank=True -在管理面板中允许空字段 null=True -将允许将null保存到数据库列。

理解Django模型字段定义中的选项(至少)有两个目的是至关重要的:定义数据库表，定义模型表单的默认格式和验证。(我说“默认”是因为可以通过提供自定义表单来覆盖这些值。)一些选项会影响数据库，一些选项会影响表单，还有一些会同时影响两者。

说到null和blank，其他答案已经说明，前者影响数据库表定义，后者影响模型验证。我认为，通过查看所有四种可能配置的用例，可以更清楚地区分它们:

null=False, blank=False: This is the default configuration and means that the value is required in all circumstances. null=True, blank=True: This means that the field is optional in all circumstances. As noted below, though, this is not the recommended way to make string-based fields optional. null=False, blank=True: This means that the form doesn't require a value but the database does. There are a number of use cases for this: The most common use is for optional string-based fields. As noted in the documentation, the Django idiom is to use the empty string to indicate a missing value. If NULL was also allowed you would end up with two different ways to indicate a missing value. (If the field is also unique, though, you'll have to use null=True to prevent multiple empty strings from failing the uniqueness check.) Another common situation is that you want to calculate one field automatically based on the value of another (in your save() method, say). You don't want the user to provide the value in a form (hence blank=True), but you do want the database to enforce that a value is always provided (null=False). Another use is when you want to indicate that a ManyToManyField is optional. Because this field is implemented as a separate table rather than a database column, null is meaningless. The value of blank will still affect forms, though, controlling whether or not validation will succeed when there are no relations. null=True, blank=False: This means that the form requires a value but the database doesn't. This may be the most infrequently used configuration, but there are some use cases for it: It's perfectly reasonable to require your users to always include a value even if it's not actually required by your business logic. After all, forms are only one way of adding and editing data. You may have code that is generating data that doesn't need the same stringent validation you want to require of a human editor. Another use case that I've seen is when you have a ForeignKey for which you don't wish to allow cascade deletion. That is, in normal use the relation should always be there (blank=False), but if the thing it points to happens to be deleted, you don't want this object to be deleted too. In that case you can use null=True and on_delete=models.SET_NULL to implement a simple kind of soft deletion.

根据文档，null真正与数据库相关。如果null=true, DB将null输入存储为null。否则，空字符串将被存储为空字符串。 然而，如果blank=true, form将验证它为ok，否则该字段将被form视为“必需”。

默认为false。

正如Django Model Field reference中所说:Link

Field options The following arguments are available to all field types. All are optional. null Field.null If True, Django will store empty values as NULL in the database. Default is False. 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. For both string-based and non-string-based fields, you will also need to set blank=True if you wish to permit empty values in forms, as the null parameter only affects database storage (see blank). Note When using the Oracle database backend, the value NULL will be stored to denote the empty string regardless of this attribute blank Field.blank If True, the field is allowed to be blank. Default is False. 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.