Question

我有以下型号：

var age = parseInt(prompt("How old are you?"), 10);

function calcDateAge(age) {
  var dateAge = Math.floor(age / 2) + 7; 
  // If age is 30, this gives 30/2 + 7 = 15 + 7 = 22. 
  // If age is 31, this gives 31/2 + 7 = 15 + 7 = 22.
  return dateAge;
}


for (i = calcDateAge(age); i > 18; i--) {
  console.log(i);
}

如何将模型class Student(AbstractUser): email = models.EmailField(unique=True) roll = models.CharField(max_length=200, blank=False, unique=True, primary_key=True) contact_no = models.DecimalField( max_digits=10, decimal_places=0, blank=False, unique=True) objects = UserManager() class Event(models.Model): type_of_event = models.ForeignKey(EventType, on_delete=models.CASCADE) name = models.CharField(max_length=100) description = models.TextField() event_date = models.DateField() venue = models.CharField(max_length=200) entry_fee = models.FloatField() def __str__(self): return self.name def get_absolute_url(self): return reverse('dashboard') class EventParticipants(models.Model): event_name = models.ForeignKey(Event, on_delete=models.CASCADE) participant_roll = models.ForeignKey( Student, on_delete=models.CASCADE, default="123")中的roll字段用作表Student中的外键。默认情况下，将模型EventParticipants中的username字段选择为外键。

Answer 1

Django文档here说，您可以在ForeignKey声明中将 to_field 值设置为目标模型中的任何唯一字段。

participant_roll = models.ForeignKey(
        Student, on_delete=models.CASCADE, to_field='roll')

如何选择另一个表的特定字段作为表的外键？ Sqlite3，Django == 2.1

1 个答案: