[英]How to join tables with multiple foreign keys and get filtered data in Django?
我有兩個這樣的模型:
class Question(models.Model):
ques_id = models.IntegerField()
test_id = models.ForeignKey('exam.Test')
ques = models.TextField()
class UserAnswer(models.Model):
user = models.ForeignKey('exam.User')
test_id = models.ForeignKey('exam.Test')
ques_id=models.ForeignKey('exam.Question')
user_ans = models.TextField()
我需要執行此查詢以獲取正確的“ ques”字段值。
SELECT A.ques_id, B.ques, A.user_ans FROM useranswer A
inner join question B on B.ques_id= A.ques_id and B.test_id =A.test_id
WHERE A.user_id=1 and B.test_id='101'
到目前為止,我已經做了:
UserAnswer.objects.filter(test_id=test_id, user_id=user_id).values('ques_id', 'ques_id__ques','user_ans')
但是它沒有返回正確的“ ques”字段值,因為它沒有考慮B.test_id = A.test_id部分。 如何找回它???
首先,您的字段名稱具有誤導性。 不要后綴外鍵的字段_id
! 將它們作為屬性訪問將返回模型實例,而django提供了_id
后綴的屬性以隱式訪問實際的鍵:
class Question(models.Model):
test = models.ForeignKey('exam.Test')
ques = models.TextField()
# is this supposed to be the primary key? Don't do that
# ques_id = models.IntegerField()
class UserAnswer(models.Model):
user = models.ForeignKey('exam.User')
ques = models.ForeignKey('exam.Question')
user_ans = models.TextField()
# This is redundant as ques belongs to a test already
# test = models.ForeignKey('exam.Test')
我假設您想獲得一位用戶和一項測試的所有答案:
UserAnswer.objects.filter(
ques__test_id=test_id,
user_id=user_id
).values('ques_id', 'ques__ques', 'user_ans')
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