diff options
Diffstat (limited to 'docs/ref/models')
| -rw-r--r-- | docs/ref/models/fields.txt | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/docs/ref/models/fields.txt b/docs/ref/models/fields.txt index a56c445c31..2435201db8 100644 --- a/docs/ref/models/fields.txt +++ b/docs/ref/models/fields.txt @@ -43,11 +43,13 @@ If ``True``, Django will store empty values as ``NULL`` in the database. Default is ``False``. Avoid using :attr:`~Field.null` on string-based fields such as -:class:`CharField` and :class:`TextField` because empty string values will -always be stored as empty strings, not as ``NULL``. If a string-based field has +:class:`CharField` and :class:`TextField`. 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 "no data;" the Django convention is to use the empty string, not +``NULL``. One exception is when a :class:`CharField` has both ``unique=True`` +and ``blank=True`` set. In this situation, ``null=True`` is required to avoid +unique constraint violations when saving multiple objects with blank values. 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 |