On Oct 15, 5:32 pm, Katja Loeffler <[EMAIL PROTECTED]> wrote:
> Hi,
>
> I am relatively new to Django and I have a small problem making a query
> over the following Models ...
>
> class GeographicTemporalCoverage(models.Model):
> beginning_temporal_coverage_date = models.DateField()
> ending_temporal_coverage_date = models.DateField()
> ....
>
> class Coverage(models.Model):
> geo_temp_coverage = models.ManyToManyField(GeographicTemporalCoverage)
> abstract = models.TextField()
> ...
>
> class DataSet(models.Model):
> ...
> dataset_id_nr = models.CharField(max_length=64)
> coverage = models.ForeignKey(Coverage)
> ...
>
> Now I want to query all DataSets having a coverage with a maximal
> ending_temporal_coverage of 2008 for example ...
>
> Can I do it in one query (how) or do I need to make two for that?
>
> I've tried something like
>
> ds =
> DataSet.objects.select_related().filter(coverage__geo_temp_coverage__ending_temporal_coverage_date<max_year).order_by('dataset_id_nr')
> but unfortunately it does not work ;).
> ( global name
> 'coverage__geo_temp_coverage__ending_temporal_coverage_date' is not defined)
> I also did not any hints in the documentation ...
>
> Thanks in advance!
> Katja
>
> --
> Computer and Database Manager
> 3193 Energy, Coast & Environment Bldg.
> Louisiana State University
> Baton Rouge, LA, 70803
You're on the right track, but you can't use operators like < and > in
a filter. You need to use __gt and __lt instead. (Inside the code it's
not an expression being evaluated, but a keyword being sent to a
function). So your query should be:
DataSet.objects.select_related().filter(coverage__geo_temp_coverage__ending_temporal_coverage_date__lt=max_year).order_by('dataset_id_nr')
If max_year is actually a year rather than a datetime, you would need
to use the __year suffix as well:
coverage__geo_temp_coverage__ending_temporal_coverage_date__year__lt=max_year
--
DR.
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