Question

对于每个问题，都有很多答案。我有一个表投票，其中包含所有问题和答案的upvote / downvotes。我想执行类似的查询：

从投票中选择* WHERE username =＆＃34; some username＆＃34; AND（QID =＆＃34;问题＆＃34; 或（AID IN（来自Answers的选择AID，QERE =＆＃34;问题＆＃34;）））

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)

P.S。请注意，QID和AID是外键。所以他们只会采用问题/答案模型的实例。

Answer 1

你可以，

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，如果您想获得问题的所有Vote个对象，那么您可以调用反向关系，例如，

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

Answer 2

我认为更好的方法是：

from django.db.models import Q

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

它避免了Fazil Zaid的答案中的额外查询，即通过在单个查询中执行此操作来获取给定问题ID的答案ID。

执行WHERE＆＃39;字段＆＃39; Django中的IN（list）查询？

2 个答案: