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June 3, 2019 14:28
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Django making queries
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| from django.db import models | |
| class Student(models.Model): | |
| name = models.CharField(max_length=30) | |
| class Exam(models.Model): | |
| name = models.ForeignKey(Student, on_delete=models.CASCADE) | |
| point = models.PositiveIntegerField(default=0) | |
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| from django.db.models import Case, IntegerField, Sum, Value, When | |
| from django.db.models.functions import Coalesce | |
| q = Exam.objects.aggregate( | |
| success=Coalesce( | |
| Sum( | |
| Case( | |
| When(score__gte=85, then=Value(1)), | |
| default=Value(0), | |
| output_field=IntegerField(), | |
| ) | |
| ), | |
| Value(0), | |
| ), | |
| ) | |
| print(q) | |
| # {"success": 5} |
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