我的模型如下:我有一组Dude
s,每个Dude
s都有一组首选项。我可以很容易地根据他们的单一偏好找到Dude
,但我需要找到那些喜欢两种不同事物的人。我试图将两个Q
对象传递给filter()
函数,但在生成的SQL中,这两个Q
对象引用了相同的相关Preference
。我希望他们指的是两个不同的Preferences
。更糟糕的是,我需要查询相关模型(=Preference
)的几个属性,所以我不能使用简单的__in
。
型号:
class Dude(models.Model):
name = models.CharField(max_length=200)
class Preference(models.Model):
name = models.CharField(max_length=200)
how_much = models.CharField(max_length=200)
dude = models.ForeignKey(Dude)
测试用例:
class DudesTestCase(TestCase):
def setUp(self):
dude = Dude.objects.create(name = 'Dude')
cheese = Preference.objects.create(name = 'Cheese', how_much = "very", dude = dude)
bacon = Preference.objects.create(name = 'Bacon', how_much = "absolutely_love", dude = dude)
# does work
def test_cheese_lovers(self):
d = Dude.objects.filter(preference__name = 'Cheese', how_much = "very")
self.assertEquals(d[0].name, 'Dude')
# does not work - wants a single Preference to be both cheese and bacon
def test_cheese_and_bacon_lovers(self):
d = Dude.objects.filter(
Q(preference__name = 'Cheese', how_much = "very"),
Q(preference__name = 'Bacon', how_much = "absolutely_love"),
)
self.assertEquals(d[0].name, 'Dude')
澄清:我不想发现男人喜欢奶酪或培根,我需要人们同时满足这两个条件。
我认为这应该能在中工作
def test_cheese_and_bacon_lovers(self):
d = Dude.objects.filter(
preference__name='Cheese',
how_much__in=("very", "absolutely_love"),
).filter(
preference__name='Bacon',
how_much__in=("very", "absolutely_love"),
)
self.assertEquals(d[0].name, 'Dude')
此处的文档中介绍了这种用法:
https://docs.djangoproject.com/en/1.8/topics/db/queries/#spanning-多值关系
向模型添加相关名称:
class Preference(models.Model):
name = models.CharField(max_length=200)
dude = models.ForeignKey(Dude, related_name='preferences')
并使用IN
和annotate
:
Dude.objects.filter(preferences__name__in=['Cheese', 'Bacon'])
.annotate(cnt=Count('preferences__name')
.filter(cnt=2)