如何使用 Django 管理外部连接、group_by 和计数

Question

使用 Django 我有以下模型：

class Player(models.Model):
    name = models.CharField(max_length=64)
    description = models.CharField(max_length=128)
    groupPlayer = models.ForeignKey(GroupPlayer)


class GroupPlayer(models.Model):
    description = models.CharField(max_length=128)
    name = models.CharField(max_length=32)

每个玩家都链接到一个组。一些组没有玩家。我的目标是在 Django 中翻译以下查询（包括 LEFT OUTER JOIN 和 Group by）：

select GroupPlayer.description, GroupPlayer.name, COUNT(Player.name) as gplayer
from (GroupPlayer LEFT OUTER JOIN Player ON GroupPlayer.id = Player.groupPlayer_id)
GROUP BY GroupPlayer.id

到目前为止我已经创建了 3 个查询集，但我无法将它们放在一起以获得我想要的结果：

   queryset_player = Player.objects.values('groupPlayer_id').annotate(total=Count('groupPlayer__id'))
   queryset_group = GroupPlayer.objects.select_retated(queryset_player)
   queryset_group2 = GroupPlayer.objects.all().prefetch_related('player_set')

任何人都可以帮助解决 LEFT OUTER JOIN、分组和计数问题？

谢谢

Answer 1

from django.db.models import Count

groups = GroupPlayer.objects.annotate(num_players=Count('player'))
groups[0].num_players

Aggragation

如何使用 Django 管理外部连接、group_by 和计数

How manage outer join, group_by and count with Django

sql

django

django-models

django-queryset