How to calculate sum and also cumulative sum in django orm

问题

I have table project, project has sub project and subproject has developers. Another table sprint, work distribute in sprint 1 2 ..n so on, Each sprint has different developers data. Now How can i calculate sum, current sprint value and percentage complete Using Django Orm.

Project has sub project foreign key

 class project(models.Model):
        title = models.CharField(max_length=150)
        project = models.ForeignKey("self", on_delete=models.CASCADE,
                             related_name="subproject", blank=True, null=True)

  Developers table

  class Developers(models.Model):
        quantity = models.FloatField(default=0.0)
        charge_rate = models.FloatField(default=0.0)
        project = models.ForeignKey("Project", on_delete=models.SET_NULL,
                                 related_name="developers",  null=True)

Table Sprint

class Sprint(models.Model):
    sprint_name = models.CharField(max_length=150)
    percentage = models.FloatField(default=0.0)

sprint data

class SprintsData(models.Model):
    sprint = models.ForeignKey(
        "project", on_delete=models.CASCADE, related_name="d",
        blank=True)
    percentage = models.FloatField(default=0.0)

This is sample data

project

id name         project
1  development  null

Sub project

id   name       project
 1  Homepage     1
 2  header       1
 3  footer       1

Developers

id   name        quantity rate  project (sub project foreign key)
1    developers   5       200    1
2    designer      5       150    2

Sprint

id     name    start_date end_date
1     sprint1    -           -

SprintsData

id    sprint  project(subproject foreign key)  percentage
 1      1          1                               5
 2      1          2                               80

Output looks like

sprint    project      sub_project   total_sum             percentage_complete current_sprint_amount
sprint1  development     Homepage   (quantity*charge_rate)         5              (total_sum)5% 
sprint1  development     Header        5*150                       80             (5*150)*80%

回答1:

The following query will return all SprintsData objects annotated with total_sum and current_sprint_amount. From this you should be able to generate your table

from django.db.models import Sum, F
SprintsData.objects.annotate(
    total_sum=Sum(F('sprint__developers__quantity') * F('sprint__developers__charge_rate'), output_field=models.FloatField())
).annotate(
    current_sprint_amount=F('total_sum') * F('percentage')
)

SprintsData.sprint is actually a foreign key to the project model which is a little confusing

The Sprint model has no relationships to any other model so I'm not sure how you would get the sprint name

来源：https://stackoverflow.com/questions/59521332/how-to-calculate-sum-and-also-cumulative-sum-in-django-orm

标签

python

django

django-models

django-rest-framework