[Django]-How to update fields in a model without creating a new record in django?

by

185👍

✅

If you get a model instance from the database, then calling the save method will always update that instance. For example:

t = TemperatureData.objects.get(id=1)
t.value = 999  # change field
t.save() # this will update only

If your goal is prevent any INSERTs, then you can override the save method, test if the primary key exists and raise an exception. See the following for more detail:

👤ars

38👍

You should do it this way ideally

t = TemperatureData.objects.get(id=1)
t.value = 999
t.save(['value'])

This allow you to specify which column should be saved and rest are left as they currently are in database.
(https://code.djangoproject.com/ticket/4102)!

👤Zaman Afzal

29👍

Sometimes it may be required to execute the update atomically that is using one update request to the database without reading it first.

Also get–set attribute–save may cause problems if such updates may be done concurrently or if you need to set the new value based on the old field value.

In such cases query expressions together with update may by useful:

TemperatureData.objects.filter(id=1).update(value=F('value') + 1)

To update multiple fields:

TemperatureData.objects.filter(id=1).update(
    value=F('value') + 1,
    another_value=F('another_value')+1
)
👤Roman-Stop RU aggression in UA

4👍

Django has some documentation about that on their website, see: Saving changes to objects. To summarize:

.. to save changes to an object that’s already in the database, use save().

👤miku

4👍

In my scenario, I want to update the status of status based on his id

student_obj = StudentStatus.objects.get(student_id=101)
student_obj.status= 'Enrolled'
student_obj.save()

Or If you want the last id from Student_Info table you can use the following.

student_obj = StudentStatus.objects.get(student_id=StudentInfo.objects.last().id)
student_obj.status= 'Enrolled'
student_obj.save()
👤Viraj Wadate

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