如何在 Django 中添加相同 model 的两个不同 integer 字段

Question

class Score(models.Model):
  Score_A=models.IntegerField()
  Score_B=models.IntegerField()

How can I put the sum of these two fields into another field?

Answer 1

The best solutions for this create a trigger in a database that stores a total of the two fields in another field.

Answer 2

I would really advise not to store the sum of the two fields, but simply annotate the queryset. That way you avoid data duplication , which will make the database slightly larger, but more important, it will be quite hard to keep the fields in sync.

from django.db.models import F

Score.objects.annotate(Score_total=F('Score_A')+F('Score_B'))

the Score objects that arise from this queryset will have an extra attribute Score_total , which is the sum of the two fields.

Note : normally the name of the fields in a Django model are written in snake_case , not PerlCase , so it should be: score_a instead of Score_A .

Answer 3

The problem with the solutions people presented is that they work with the database, This adds some overhead, You want to do something like this

class Score(models.Model):
    Score_A = models.IntegerField()
    Score_B = models.IntegerField()

    def overall_score(self):
        return self.Score_A + self.Score_B

This won't alter the database, This may have some side effects like RACE CODITIONS , Be sure to use select_for_update or whatever way you prefer to lock the DB when using the Score model.

I'd like to mention that you should stick with pep8, score_a , score_b

Answer 4

You can override the save method so when a record is created or updated the value of the sum will be saved like below

class Score(models.Model):
  Score_A=models.IntegerField()
  Score_B=models.IntegerField()
  sum=models.IntegerField()
 def save(self, *args, **kwargs):
        self.sum = self.Score_A +self.Score_B
        super(Score, self).save(*args, **kwargs)