Objects聚合分组，统计结果个数（Count）

参考：http://python.usyiyi.cn/django/topics/db/aggregation.html

from django.db.models import Count

today = datetime.datetime.now()
p1 = datetime.timedelta(days=1)
users_today = lockoutusers.objects.filter(lockouttime__range=[(today-p1).date(),(today+p1).date()]) #获取当天的item记录

users_today.values('sAMAccountName').annotate(num=Count('sAMAccountName')) #对sAMAccountName字段进行分组，并得出个数

返回结果：

[{'num': 1, 'sAMAccountName': u'zhongwenming'}, {'num': 1, 'sAMAccountName': u'sunqian'},...(remaining elements truncated)...']

假设有以下 model:

class Foobar(models.Model):
    name = models.CharField(max_length=100)
    date_created = models.DateField(auto_now_add=True)

    def __unicode__(self):
        return self.name

按天统计数量的代码如下：

from django.db import connection
from django.db.models import Count

select = {'day': connection.ops.date_trunc_sql('day', 'date_created')}
Foobar.objects.extra(select=select).values('day').annotate(number=Count('id'))
# [{'number': 10, 'day': datetime.datetime(2013, 9, 29, 0, 0, 0}]