I can't wrap my head how to store / define the right model / relationship.

I have following data:

CATEGORY is their own model because i like to view / request in some situation only the category. But to this category I want set VALUE which I can only define onetime depending ON YYYY-MM.

What make me difficult to achieve / understand how i get the relationship between VALUE <-> YYYY-MM but still maintain the connection / dependency to only one CATEGORY "Rent".

CodePudding user response：

I would look at doing something like this. You have two models with a foreign key, and value and YYYY-MM are attributes of the model with the foreign key.

class Category(models.model):
  pass

class TimePeriod(models.Model):
    category = models.ForeignKey(Category, on_delete=models.CASCADE)
    value = models.IntegerField()
    start_date = models.DateField()

    class Meta:
        constraints = [
            models.UniqueConstraint(
                fields=["category", "start_date"], 
                name="unique_start_date_per_category"
            ),
        ]

EDIT: Add UniqueConstraint