  class Article(models.Model):
      Article_ID = models.AutoField(primary_key=True, db_column='Article ID')
      headline = models.CharField(max_length=100)
      authors = models.ManyToManyField(Author, db_table='my_m2m_table')
      primary_author = models.ForeignKey(Author, db_column='Author ID', related_name='primary_set', null=True)
  
      def __str__(self):
          return self.headline
  
      class Meta:
 
</s> remove     reporter = models.ForeignKey(Reporter)
    response_to = models.ForeignKey('self', null=True)
 </s> add     reporter = models.ForeignKey(Reporter, models.CASCADE)
    response_to = models.ForeignKey('self', models.SET_NULL, null=True) </s> remove     reporter = models.ForeignKey(Reporter, null=True)
 </s> add     reporter = models.ForeignKey(Reporter, models.SET_NULL, null=True) </s> remove     reporter = models.ForeignKey(Reporter)
    reporter_proxy = models.ForeignKey(ReporterProxy, null=True,
                                       related_name='reporter_proxy')
 </s> add     reporter = models.ForeignKey(Reporter, models.CASCADE)
    reporter_proxy = models.ForeignKey(
        ReporterProxy,
        models.SET_NULL,
        null=True,
        related_name='reporter_proxy',
    ) </s> remove     author = models.ForeignKey(Author)
 </s> add     author = models.ForeignKey(Author, models.CASCADE) </s> remove     author = models.ForeignKey(Author)
    book = models.ForeignKey(Book)
 </s> add     author = models.ForeignKey(Author, models.CASCADE)
    book = models.ForeignKey(Book, models.CASCADE)
    primary_author = models.ForeignKey(
        Author,
        models.SET_NULL,
        db_column='Author ID',
        related_name='primary_set',
        null=True,
    )
  class Article(models.Model):
      Article_ID = models.AutoField(primary_key=True, db_column='Article ID')
      headline = models.CharField(max_length=100)
      authors = models.ManyToManyField(Author, db_table='my_m2m_table')
    primary_author = models.ForeignKey(
        Author,
        models.SET_NULL,
        db_column='Author ID',
        related_name='primary_set',
        null=True,
    )
  
      def __str__(self):
          return self.headline
  
      class Meta:
keep keep keep keep replace keep keep keep keep keep
 Fixed #21127 -- Started deprecation toward requiring on_delete for ForeignKey/OneToOneField 
tests/custom_columns/models.py