My goal is to get a list of unique countries referenced through a
table. My model has:
class Country(models.Model):
Abbreviation = models.CharField(maxlength = 2, primary_key=True)
Country = models.CharField(maxlength = 50)
class TrainingEvent(models.Model):
Country = models.ForeignKey(Country)
Partner = models.ForeignKey(Partner)
City = models.CharField(maxlength = 50)
Course_Title = models.CharField(maxlength = 80)
class EventDates(models.Model):
TrainingEvent = models.ForeignKey(TrainingEvent)
Event_Start = models.DateField(core = True)
Event_Dates = models.CharField(core = True, maxlength = 30)
I only want a list of countries that are referenced for a
TrainingEvent whose Event_Start__range=(begin,end)
>>> eds = EventDates.objects.filter(Event_Start__range=(start,end)
>>> eds
[<EventDates: June 25th - 28th>, <EventDates: July 2nd - 5th>,
<EventDates: July 23rd - 25th>, <EventDates: Aug 6th - 9th>,
<EventDates: July 9th - 10th>, <EventDates: July 23rd - 24th>]
>>> eds.values('TrainingEvent').distinct()
[{'TrainingEvent': 1L}, {'TrainingEvent': 2L}]
>>> eds.values('TrainingEvent.Country')
FieldDoesNotExist: EventDates has no field named
'TrainingEvent.Country'
>>> eds.values('TrainingEvent_Country')
FieldDoesNotExist: EventDates has no field named
'TrainingEvent_Country'
>>> eds.values('TrainingEvent__Country')
FieldDoesNotExist: EventDates has no field named
'TrainingEvent__Country'
Again, my goal is to be able to show each Country that has a
TrainingEvent that has an Event_Start between start and end. There are
probably many ways to get there. I'm very used to SQL and could do
this in a heartbeat that way, but I want to learn the Django way.
On a related note, I often would like to do something like:
SELECT * FROM other_table WHERE some_value in ('a','b','c');
The way that seems logical to me is to do:
values = TableName.objects.values('id').filter(...)
t = OtherTable.objects.filter(TableName__in=values)
I've tried several permutations of this and haven't found anything
that works. What is the correct way to do this?
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