CODEWITHSUNDEEP
djangomodel
Chris Muench
Chris Muench

Reputation: 18338

django ForeignKey null = true

from django.db import models

class Story(models.Model):
    id = models.IntegerField(primary_key=True)
    news_type = models.CharField(max_length=255,null=True)
    category_id = models.CharField(max_length=255,null=True)
    title = models.CharField(max_length=255,null=True)
    created = models.DateTimeField(null=True)
    author = models.CharField(max_length=255, null=True)
    author_title = models.CharField(max_length=255, null=True)
    image_caption = models.TextField(null=True)
    image_credit = models.CharField(max_length=255,null=True)
    image_full_url = models.CharField(max_length=255,null=True)
    body = models.TextField(null=True)
    summary = models.TextField(null=True)
    video_id = models.CharField(max_length=255,null=True)
    external_url = models.CharField(max_length=255,null=True)
    order = models.IntegerField(null=True)

class StoryFactBox(models.Model):
    story = models.ForeignKey('Story', null = True)
    body = models.TextField()

class StoryKeyword(models.Model):
    story = models.ForeignKey('Story', null = True)
    keyword = models.CharField(max_length=255)

What schema changes does models.ForeignKey('Story', null = True) cause to happen?

I am reading from the docs:

I want to use remove() and clear() and this is part of documentation.

In order to prevent database inconsistency, this method only exists on ForeignKey objects where null=True. If the related field can't be set to None (NULL), then an object can't be removed from a relation without being added to another. In the above example, removing e from b.entry_set() is equivalent to doing e.blog = None, and because the blog ForeignKey doesn't have null=True, this is invalid.

Upvotes: 3

Views: 11162

Answers (1)

Yuji 'Tomita' Tomita
Yuji 'Tomita' Tomita

Reputation: 118528

It causes no changes to the schema (just clarifying it only creates tables, doesn't modify), but upon syncdb, would create SQL statements without NOT NULL.

You can check the SQL output of the table definitions via python manage.py sqlall my_app and see for yourself!

Upvotes: 4

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