How to fetch object with multiple levels of reverse lookup

Question

In my project, there are three models:

class Level1(models.Model):
        name = models.CharField(max_length=250)


class Level2(models.Model):
        name = models.CharField(max_length=250)
        level1 = models.ForeignKey(Level1, on_delete=models.RESTRICT)

class Level3(models.Model):
        name = models.CharField(max_length=250)
        level2 = models.ForeignKey(Level2, on_delete=models.RESTRICT)

Level1 model has 2 objects WA, TX. Level2 has 5 objects AAA, BBB where the foreign key is WA; and AAA, CCC, DDD where the foreign key is TX.

In Level3, I want to add an object RRRR where the Level2 foreign key object is AAA.

When I tried to fetch the Level2 by Level2.objects.get(name='AAA'), it shows error get() returned more than one Level2 -- it returned 2!

How to solve this issue. Thanks in advance.

you filter level 2 by name attribute which isn't unique – Dimitris Kougioumtzis Jun 18 '21 at 18:07 — Dimitris Kougioumtzis, Jun 18 '21 at 18:07

score 0 · Answer 1 · answered Jun 18 '21 at 15:22

0

yes this is because get method will allow to retrieve only one object you can use

Level2.objects.filter(name='AAA')

answered Jun 18 '21 at 15:22

steve harvey

110
7

this will retrieve 2 level2 objects, bother are foreign keyed to different level1 object. I want to add one object in Level3 model. – Bayezid Talukdar Jun 18 '21 at 15:36

score 0 · Answer 2 · answered Jun 18 '21 at 15:38

0

get expects to find only one object and will error otherwise. You can add more lookups

Level2.objects.filter(name='AAA', level1__name='WA') or 
Level2.objects.filter(name='AAA', level1__name='TX')

answered Jun 18 '21 at 15:38

Mark Rofail

808
1
8
18

It shows, "The QuerySet value for an exact lookup must be limited to one result using slicing.". – Bayezid Talukdar Jun 18 '21 at 15:49

score 0 · Accepted Answer · answered Jun 18 '21 at 18:08

0

Alhamdulillah, finally I solve the issue by combining filter and get.

Level2.objects.filter(level1__name='WA').get(name='AAA')

answered Jun 18 '21 at 18:08

Bayezid Talukdar

1
2

How to fetch object with multiple levels of reverse lookup

3 Answers3