Django models many to many relations - django

Question

I'm moving my first steps with django and I'm trying to figure out a thing.
Suppose that we have a model.py made like this where NameEffect has a many to many relation
class Name(models.Model):
nameid = models.IntegerField()
name = models.CharField(max_length=255)
class Effect(models.Model):
effectid = models.IntegerField()
effect = models.TextField()
class NameEffect(models.Model):
nameid = models.IntegerField()
effectid = models.IntegerField()
start = models.PositiveIntegerField()
strand = models.PositiveIntegerField()
and I want to create a QuerySet where every entry contains name,effect,start,strand of the researched name. Fact is that the only solution I found was using raw SQL queries but I can't understand how to do it with the django models approach

Answer 1

You haven't defined any relationships here at all. You should identify the fields as ForeignKeys - and also define the implicit many-to-many relationship explicitly (although you don't actually need it for this particular query, but it'll definitely come in useful).
class Name(models.Model):
nameid = models.IntegerField(primary_key=True)
name = models.CharField(max_length=255)
effects = models.ManyToManyField('Effect', through='NameEffect')
class Effect(models.Model):
effectid = models.IntegerField(primary_key=True)
effect = models.TextField()
class NameEffect(models.Model):
name = models.ForeignKey('Name', db_column='nameid')
effect = models.ForeignKey('Effect', db_column='effectid')
start = models.PositiveIntegerField()
strand = models.PositiveIntegerField()
Now you can can query NameEffect directly to get the result you want.
data = NameEffect.objects.values('name__name', 'effect__effect', 'start', 'strand')
Also note, unless you know you really need just these fields, you should avoid using values and just query NameEffect using select_related:
name_effects = NameEffect.objects.select_related('name', 'effect')
and then access the values when you need them, eg in a template:
{% for obj in name_effects %}
{{ obj.name.name }}
{{ obj.effect.effect }}
{{ obj.start }}
{{ obj.strand }}
{% endif %}