Data Model:
class A(models.model):
desc: model.CharField()
class B(models.model):
a: model.ForeignKey('A')
desc: models.CharField()
I need to do this select in a view:
select max(num_a) as max_num_a from (select a, count(desc) as
num_a
from B group by a) as x;
I've tried this:
result =
B.objects.values('a').annotate(num_a=Count('a')).aggregate(Max('num_a'))
And I got this error:
1064, "You have an error in your SQL syntax; check the manual that
corresponds to your MySQL server version for the right syntax to use
near 'FROM (SELECT `B`.a` AS `a`, COUNT(`a' at line 1")
If we only group and not obtain max it works:
result = B.objects.values('a').annotate(num_a=Count('a'))
and the result is : {'a': 1L, 'num_a': 9}{'a': 2L, 'num_a': 6}{'a':
3L,
'num_a': 4}
I'm not sure what I'm doing wrong, neither if there's other way to
resolve it.
If somebody have been faced with and resolved it, I'll be gratefull if
he can show me how can I start for beating this.
Thanks all.
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