I want to sort models by day first and then by score, meaning I'd like to see the the highest scoring Articles in each day.

class Article(models.Model):date_modified = models.DateTimeField(blank=True, null=True)
score = models.DecimalField(max_digits=5, decimal_places=3, blank=True, null=True)

This answer Django Datetime Field Query - Order by Time/Hour suggests that I use '__day' with my date_modified as in:

Article.objects.filter().order_by('-date_modified__day', '-score')
FieldError: Cannot resolve keyword 'day' into field. Join on 'date_modified' not permitted.

However I get the same error as in the post, so I'm not even sure it should work this way.

I found other answers django order by date in datetime / extract date from datetime using .extra:

Article.objects.filter().extra(select={"day_mod": "strftime('%d', date_modified)"}, order_by=['-day_mod', '-score'])

This works for filtering with no other conditions, but if I apply a condition on the filter such as a category:

Article.objects.filter(category = 'Art').extra(select={'day_mod': "strftime('%d', date_modified)"}, order_by=['-day_mod', '-score'])

I get this error:

File "/home/mykolas/anaconda2/lib/python2.7/site-packages/IPython/core/formatters.py", line 699, in __call__
printer.pretty(obj)File "/home/mykolas/anaconda2/lib/python2.7/site-packages/IPython/lib/pretty.py", line 383, in pretty
return _default_pprint(obj, self, cycle)File "/home/mykolas/anaconda2/lib/python2.7/site-packages/IPython/lib/pretty.py", line 503, in _default_pprint
_repr_pprint(obj, p, cycle)File "/home/mykolas/anaconda2/lib/python2.7/site-packages/IPython/lib/pretty.py", line 694, in _repr_pprint
output = repr(obj)File "/home/mykolas/lenv/lib/python2.7/site-packages/django/db/models/query.py", line 234, in __repr__
data = list(self[:REPR_OUTPUT_SIZE + 1])File "/home/mykolas/lenv/lib/python2.7/site-packages/django/db/models/query.py", line 258, in __iter__
self._fetch_all()File "/home/mykolas/lenv/lib/python2.7/site-packages/django/db/models/query.py", line 1074, in _fetch_all
self._result_cache = list(self.iterator())File "/home/mykolas/lenv/lib/python2.7/site-packages/django/db/models/query.py", line 52, in __iter__
results = compiler.execute_sql()File "/home/mykolas/lenv/lib/python2.7/site-packages/django/db/models/sql/compiler.py", line 848, in execute_sql
cursor.execute(sql, params)File "/home/mykolas/lenv/lib/python2.7/site-packages/django/db/backends/utils.py", line 83, in execute
sql = self.db.ops.last_executed_query(self.cursor, sql, params)File "/home/mykolas/lenv/lib/python2.7/site-packages/django/db/backends/sqlite3/operations.py", line 146, in last_executed_query
return sql % paramsTypeError: %d format: a number is required, not unicode

Don't really know what's going on here, help would be appreciated.

from django.db.models import DateTimeField
from django.db.models.functions import TruncArticle.objects.order_by(Trunc('date_modified', 'date', output_field=DateTimeField()).desc(),'-score')

• Trunc() (Django 1.10)
• order_by()