Question

这是我的模特

class Stockdata(models.Model):
    stock_name  = models.CharField(max_length=32,unique=True)

class Stock_Total_sales(models.Model):
    sales       = models.ForeignKey(Sales,on_delete=models.CASCADE,null=True,blank=False,related_name='saletotal')
    stockitem   = models.ForeignKey(Stockdata,on_delete=models.CASCADE,null=True,blank=True,related_name='salestock') 
    quantity    = models.PositiveIntegerField()

class Stock_Total(models.Model):
    purchases   = models.ForeignKey(Purchase,on_delete=models.CASCADE,null=True,blank=False,related_name='purchasetotal') 
    stockitem   = models.ForeignKey(Stockdata,on_delete=models.CASCADE,null=True,blank=True,related_name='purchasestock') 
    quantity_p  = models.PositiveIntegerField()

我想计算购买和销售的数量，并在带注释的值之间进行减法。

所以，我这样做了：

        qs = Stockdata.objects.annotate(
        sales_sum = Subquery(
            Stock_Total_sales.objects.filter(
                sales = OuterRef('pk')
                ).values(
                    'sales'
                ).annotate(
                    the_sum = Sum('quantity')
                ).values('the_sum')
            ),
        purchase_sum = Coalesce(Sum('purchasestock__quantity_p'),0)
    )
    qs1 = qs.annotate(
        difference = ExpressionWrapper(F('purchase_sum') - F('sales_sum'), output_field=DecimalField())

但是sales_sum的值即将到来NONE子查询或其他任何问题吗？

任何人都可以告诉我我在代码中犯了什么错误。

谢谢

DJANGO：执行子查询后，注释的值将为NONE

0 个答案: