[英]Joining multiple tables for a single report in Django
From the example dataset below, how would I query, either through django.db or through the database API to get the request result? 从下面的示例数据集中,如何通过django.db或数据库API查询以获得请求结果?
I want to query the data set to get all items new than a specified date in A, but I only want the name and color from B and the taste from C. 我想查询数据集,以获取比A中指定日期新的所有商品,但我只希望B中的名称和颜色以及C中的味道。
class A(models.Model):
export_date = models.DateField()
class B(models.Model):
name = models.CharField()
color = models.CharField()
weight = models.CharField()
a = models.ForeignKey(A)
class C(models.Model):
taste = models.CharField()
smell = models.CharField()
a = models.ForeignKey(A)
EDIT: I can do 编辑:我可以做
as = A.objects.all().filter(export_date__gte=date)
b = B.objects.all().filter(a=as)
c = B.objects.all().filter(c=as)
but then I'm still stuck with two separate query sets that I have to figure out how to manually join. 但是后来我仍然遇到两个单独的查询集,我必须弄清楚如何手动加入。
class A(models.Model):
export_date = models.DateField()
class B(models.Model):
name = models.CharField()
color = models.CharField()
weight = models.CharField()
a = models.ForeignKey(A, related_name='bs')
class C(models.Model):
taste = models.CharField()
smell = models.CharField()
a = models.ForeignKey(A, related_name='cs')
as_result = A.objects.filter(export_date__gte=date)
for a in as_result:
for b in a.bs:
print b.name
print b.color
for c in a.cs:
print c.taste
If you don't have more than one B and C for each A, consider using OneToOne relationships. 如果每个A的B和C不超过一个,请考虑使用OneToOne关系。
Try the following: 请尝试以下操作:
from django.db import models
class A(models.Model):
export_date = models.DateField()
def __unicode__(self):
return "date: {0}".format(self.export_date)
class B(models.Model):
name = models.CharField(max_length=255)
color = models.CharField(max_length=255)
weight = models.CharField(max_length=255)
a = models.ForeignKey(A)
def __unicode__(self):
return "name: {0}, color: {1}, weight: {2}".format(self.name,
self.color,
self.weight)
class C(models.Model):
taste = models.CharField(max_length=255)
smell = models.CharField(max_length=255)
a = models.ForeignKey(A)
def __unicode__(self):
return "taste: {0}, smell: {1}".format(self.taste, self.smell)
from django.contrib import admin
from .models import *
admin.site.register(A)
admin.site.register(B)
admin.site.register(C)
from myapp.models import A, B, C
A.objects.values('b__color', 'c__taste', 'c__smell')\
.order_by('id') \
.distinct()
A: A:
- date: 2015-06-10
- date: 2015-06-09
B: B:
- (A: 2015-06-09) name: name 2, color: white, weight: 10 kg
- (A: 2015-06-09) name: name 1, color: black, weight: 1 kg
C: C:
- (A: 2015-06-09) taste: vanilla, smell: peppermint
- (A: 2015-06-09) taste: pizza, smell: coffee
[
{'b__color': u'black', 'c__taste': u'pizza', 'c__smell': u'coffee'},
{'b__color': u'black', 'c__taste': u'vanilla', 'c__smell': u'peppermint'},
{'b__color': u'white', 'c__taste': u'pizza', 'c__smell': u'coffee'},
{'b__color': u'white', 'c__taste': u'vanilla', 'c__smell': u'peppermint'},
{'b__color': None, 'c__taste': None, 'c__smell': None}
]
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