django如何使用外键注释

Question

考虑简单的Django模型

class Journey(models.Model):
    vrn=models.CharField(max_length=200) # Vehicle Reg No
    kilo=models.FloatField()

class J_user(models.Model):
    jdi=models.ForeignKey(Journey, related_name="Journey_User",on_delete = models.DO_NOTHING,)
    uid=models.IntegerField()

很容易在一个表中进行注释，就像我们想要每辆车的行驶总里程（vrn代表车辆的注册号）

Journey.objects.values('vrn').annotate(Total_kilo=Sum('kilo'))

现在，我想查询一个查询，该查询将返回每个用户在每辆汽车中行驶了多少公里。

“旅程数据表”

J_user表的数据

那么结果应该是

感谢您的帮助。

Answer 1

这是您的查询：

Journey
.objects
.order_by()   #<-- important to avoid include sort fields
.values('vrn', 'j_user__uid', )
.annotate(Total_kilo=Sum('kilo'))

values上的字段将包含在聚合子句中。样本：

print(
    Material
    .objects
    .values( "uf_id", "uf__mp__id", )
    .annotate( Sum("total_social_per_c") )
    .query )

结果：

SELECT "material_material"."uf_id", 
       "ufs_uf"."mp_id", 
       Sum("material_material"."total_social_per_c") AS 
       "total_social_per_c__sum" 
FROM   "material_material" 
       INNER JOIN "ufs_uf" 
               ON ( "material_material"."uf_id" = "ufs_uf"."id" ) 
GROUP  BY "material_material"."uf_id", 
          "ufs_uf"."mp_id" 

Answer 2

根据您的模型，它应该是：

topics = c.classify("what about ")
if "resources" in topics:
    print("yes")