我对Django查询模型有疑问。我知道如何编写简单的查询,但我不熟悉两个表上的LEFT JOIN。所以你能否就他的问题给我一些建议,以便更好地理解DJango ORM。
select
count(ips.category_id_id) as how_many,
ic.name
from
izibizi_category ic
left join
izibizi_product_service ips
on
ips.category_id_id = ic.id
where ic.type_id_id = 1
group by ic.name, ips.category_id_id
从这个查询我得到结果:
How many | name
0;"fghjjh"
0;"Papir"
0;"asdasdas"
0;"hhhh"
0;"Boljka"
0;"ako"
0;"asd"
0;"Čokoladne pahuljice"
0;"Mobitel"
2;"Čokolada"
我也尝试过他的Django查询:
a = Category.objects.all().annotate(Count('id__category',distinct=True)).filter(type_id=1)
但没有结果。
我的模特:
class Category(models.Model):
id = models.AutoField(primary_key=True)
type_id = models.ForeignKey('CategoryType')
name = models.CharField(max_length=255)
def __str__(self):
return str(self.name)
class Product_service(models.Model):
id = models.AutoField(primary_key=True)
name = models.CharField(max_length=255, blank=True, null=True)
selling_price = models.DecimalField(decimal_places=5, max_digits=255, blank=True, null=True)
purchase_price = models.DecimalField(decimal_places=5, max_digits=255, blank=True, null=True)
description = models.CharField(max_length=255, blank=True, null=True)
image = models.FileField(upload_to="/", blank=True, null=True)
product_code = models.CharField(max_length=255, blank=True, null=True)
product_code_supplier = models.CharField(max_length=255, blank=True, null=True)
product_code_buyer = models.CharField(max_length=255, blank=True, null=True)
min_unit_state = models.CharField(max_length=255, blank=True, null=True)
state = models.CharField(max_length=255, blank=True, null=True)
vat_id = models.ForeignKey('VatRate')
unit_id = models.ForeignKey('Units')
category_id = models.ForeignKey('Category')
如果你能帮我解决这个问题。
答案 0 :(得分:1)
您应该在category_id字段中添加相关名称,如:
category_id = models.ForeignKey('Category', related_name="product_services")
以便您可以在查询中执行以下操作:
a = Category.objects.all().annotate(Count('product_services',distinct=True)).filter(type_id=1)
然后您可以访问个人计数:
a[0].product_services__count