django-signals vs triggers?

Question

I read about django signals (http://docs.djangoproject.com/en/dev/topics/signals/), but as far as I understand, signals are never converted into literal SQL triggers (http://en.wikipedia.org/wiki/Database_trigger).

If I'm correct that signals and triggers are different, then which one is better and in what ways? What's the best practice?

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Here's a concrete example if you want one:

class Location(models.Model):
    name = models.CharField(max_length=30)

class Person(models.Model):
    location = models.ForeignKey('Location')

class Team(models.Model):
    locations = models.ManyToManyField('Location')

I want a person to be able to join a team if and only if that person's location is within that team's set of locations. I do not know how to do that with normal relational constraints, so as far as I know I'm forced to use triggers or signals. My gut says that I should use triggers but I want to know best practice.

Answer 1

Neither. The best tool for this job is model validation - you can write your custom validation rule there and it will be enforced in the admin and your own apps.