mysql - 在 Django 中执行 WHERE 'field' IN (list) 查询？

Question

每个问题都有很多答案。我有一个投票表，其中包含所有问题和答案的赞成/反对票。我想执行如下查询:

Select * from vote WHERE username="some username" AND (QID="question" OR (AID IN (SELECT AID from Answers WHERE QID="question")))

class Question(models.Model):
    QID = models.CharField( default="",max_length=5, primary_key=True)
    title = models.CharField(max_length=30, default="")
    description = models.CharField(max_length=1055, default="")
    date = models.DateTimeField(default=datetime.now, blank=True)
    username = models.CharField(max_length=30, default="")
    votes = models.IntegerField(default=0)
    approved = models.BooleanField(default=False)

    def __str__(self):
        return self.title


class Answer(models.Model):
    AID = models.CharField(max_length=5, default="", primary_key=True)
    QID = models.ForeignKey(Question,on_delete=None)
    description = models.CharField(max_length=1055, default="")
    date = models.DateTimeField(default=datetime.now, blank=True)
    username = models.CharField(max_length=30, default="")
    votes = models.IntegerField(default=0)
    approved = models.BooleanField(default=False)

    def __str__(self):
        return self.AID

class Vote(models.Model):
    username = models.ForeignKey(User,on_delete=None)
    QID = models.ForeignKey(Question,on_delete=None, null=True, blank=True)
    AID = models.ForeignKey(Answer,on_delete=None, null=True, blank=True)
    vote = models.BooleanField(default=True)

    def __str__(self):
        if self.QID is not None:
            return self.QID.QID+'_'+self.username.username+'_'+str(self.vote)
        else:
            return self.AID.AID+'_'+self.username.username+'_'+str(self.vote)

附注请注意，QID 和 AID 是外键。因此他们只会采用问题/答案模型的实例。

Answer 1

你可以做到，

from django.db.models import Q

Vote.objects.filter(username='some_username').filter(
                        Q(QID=question_id) |
                        Q(AID__QID=question_id
                        )

注意:完全同意@schillingt的回答。

或者，如果您想获取问题的所有 Vote 对象，那么您可以调用反向关系，例如，

question = Question.objects.get(QID='some_id')
question.vote_set.all()