通过django orm计数(*)来制作组

Question

使用以下型号:

class Day(models.Model):
    date = models.DateField(
        unique=True,
        null=False,
        blank=False,
    )


class Reservation(models.Model):
    user = models.ForeignKey(
        User,
        null=False,
        blank=False,
        related_name='reservations',
        verbose_name=_('Utilisateur'),
    )
    day = models.ForeignKey(
        Day,
        null=False,
        blank=False,
        related_name='reservations',
    )

要获得预订数量低于或等于5的天数,我会:

SELECT day_id
FROM meal_reservation
GROUP BY day_id
HAVING count(*) <= 5

但是如何使用Django ORM呢？

Answer 1

阅读有关使用值+注释的组合的文档,这是您需要的:

Reservation.objects.values('day').annotate(cnt=models.Count('id')).filter(cnt__lte=5)