Question

我有以下型号：

class Item(models.Model):
    closed = models.DateTimeField(blank=True, null=True)
    closed_by = models.ForeignKey(User, blank=True, null=True)

class Letter(models.Model):
    item = models.ForeignKey(Item)
    created = models.DateTimeField(default=datetime.now)
    letter_name = models.CharField(max_length=40)
    file_name = models.CharField(max_length=40, blank=True, null=True)
    deleted = models.DateTimeField(blank=True, null=True)
    deleted_by = models.ForeignKey(User, blank=True, null=True)

    def lastVersion(self):
    return self.letterversion_set.order_by('created').latest().created

class LetterVersion(models.Model):
    letter = models.ForeignKey(Letter)
    created = models.DateTimeField(default=datetime.now)
    created_by = models.ForeignKey(User)
    text = models.TextField()

    def letterItem(self):
    return self.letter.item

编辑Letter时，会创建新的Letter Version。我正在尝试使用Letter选择最近编辑过的最近3个LetterVersion.create。我的views.py：

中有以下内容

lettersAll = Letter.objects.filter(item=i_iID,deleted__isnull=True).order_by('-letterversion__created')[:3]

不幸的是，即使它们来自同一个LetterVersion，这也会让我获得基于其创建日期/时间的最后3 Letter。

letter 1 version 3 [1]
letter 3 version 4 [2]
letter 1 version 2 [3]
letter 1 version 1
letter 2 version 2
letter 2 version 1
letter 3 version 3
letter 3 version 2
letter 3 version 1

我想要的地方：

letter 1 version 3 [1]
letter 3 version 4 [2]
letter 2 version 2 [3]

无论如何，我可以获得编辑的最后3个字母的列表吗？

Answer 1

您可annotate() Max() letterversion__created，然后order_by()。{/ p>

from django.db.models import Max

lettersAll = Letter.objects.filter(
        item=i_iID,
        deleted__isnull=True
    ).annotate(
        last_created_version=Max('letterversion_created')
    ).order_by('-last_created_version')[:3]

Django：选择模型并按子模型排序可创建细节

1 个答案: