没有外键的Django-queryset加入 [英] Django-queryset join without foreignkey

问题描述

model.py

class Tdzien(models.Model):
  dziens = models.SmallIntegerField(primary_key=True, db_column='DZIENS')
  dzienrok = models.SmallIntegerField(unique=True, db_column='ROK')


class Tnogahist(models.Model):
  id_noga = models.ForeignKey(Tenerg, primary_key=True, db_column='ID_ENERG')
  dziens = models.SmallIntegerField(db_column='DZIENS')

我想要得到的是id_noga，其中dzienrok = 1234。我知道dziens应该是

What I want is to get id_noga where dzienrok=1234. I know that dziens should be

dziens = models.ForeignKey(Tdzien)

但这不是，我无法更改。通常我会使用类似的东西

but it isn't and I can't change that. Normally I would use something like

Tnogahist.objects.filter(dziens__dzienrok=1234)

，但我不知道如何在没有外键的情况下联接和过滤这些表。

but I don't know how to join and filter those tables without foreignkey.

推荐答案

可以通过执行原始sql查询来联接两个表。

It's possible to join two tables by performing a raw sql query. But for this case it's quite nasty, so I recommend you to rewrite your models.py.

您可以检查如何执行此操作此处

You can check how to do this here

像这样：

from django.db import connection

def my_custom_sql(self):
    cursor = connection.cursor()    
    cursor.execute("select id_noga
                    from myapp_Tnogahist a
                    inner join myapp_Tdzien b on a.dziens=b.dziens
                    where b.dzienrok = 1234")
    row = cursor.fetchone()
    return row

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