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Django Model Field: DateTimeField auto_now vs auto_now_add

class Task(models.Model):
    title = models.CharField(max_length=100)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

# Prasath creates a task:
task = Task.objects.create(title='Complete Django project')
print(f"Created: {task.created_at}")
print(f"Updated: {task.updated_at}")

# After 1 hour, Prasath updates the task:
task.title = 'Complete Django project - Updated'
task.save()
print(f"Created: {task.created_at}")
print(f"Updated: {task.updated_at}")

  1. Both created_at and updated_at will have the same value after the update because they are both set at creation time.

  2. created_at remains unchanged (set only at creation), but updated_at is updated to the current time with each save() call.

  3. Both fields will be updated to the current time because auto_now and auto_now_add both update on every save.

  4. updated_at will remain unchanged because auto_now only works on the first save.

Show answer & explanation

Correct answer

created_at remains unchanged (set only at creation), but updated_at is updated to the current time with each save() call.

Explanation

auto_now_add sets the field only on creation, while auto_now updates the field every time the model is saved. Therefore, created_at remains unchanged but updated_at reflects the new save time.

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All 30 Django Models and Database Design questions

  1. 1.What is the primary purpose of Django Models?
  2. 2.Which field type should be used to store an email address in a Django Model?
  3. 3.What does the Meta class inside a Django Model do?
  4. 4.Which relationship type is used when one model can have many instances of another model?
  5. 5.What is the purpose of the `__str__` method in a Django Model?
  6. 6.Which field attribute makes a field mandatory in Django Models?
  7. 7.What does the `on_delete` parameter do in a ForeignKey relationship?
  8. 8.Which of the following is a valid Django field type for storing boolean values?
  9. 9.What is the default behavior when you don't specify `null=True` for a field in Django?
  10. 10.Which method is used to retrieve a single object from the database in Django?
  11. 11.Understanding Django Model Meta Options
  12. 12.Scenario:
  13. 13.Django QuerySet Filter vs Get Method
  14. 14.Coding:
  15. 15.Scenario:
  16. 16.Understanding Django Model Inheritance
  17. 17.Coding:
  18. 18.Scenario:
  19. 19.Django Model Manager and QuerySet Methods
  20. 20.Coding:
  21. 21.Django Model Inheritance Strategy Selection
  22. 22.Django QuerySet Optimization with select_related vs prefetch_related
  23. 23.Django Model Field Choices and Validation
  24. 24.Django Model Relationships:
  25. 25.Django Model Signals and Database Consistency
  26. 26.Django Model Meta Options:
  27. 27.Django Model Managers and Custom QuerySets
  28. 28.Django Model Field:
  29. 29.Django Model Validation:
  30. 30.Django Model Aggregation and Annotation