# Help crafting Django ORMese

**URL:** <https://forum.djangoproject.com/t/help-crafting-django-ormese/1123>\
**Category:** Using Django\
**Created:** [February 10, 2020, 4:44pm UTC](https://forum.djangoproject.com/t/help-crafting-django-ormese/1123 "2020-02-10T16:44:29Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![takkaria](https://sea2.discourse-cdn.com/flex026/user_avatar/forum.djangoproject.com/takkaria/32/288_2.png) [@takkaria](https://forum.djangoproject.com/u/takkaria)\
**Post date:** [February 10, 2020, 4:44pm UTC](https://forum.djangoproject.com/t/help-crafting-django-ormese/1123/1 "2020-02-10T16:44:30Z")

</div>

Hi, I’m looking for help with some ORMese for something that would be fairly straightforward in plain SQL. Given the following models…

```auto
class Event(models.Model):
    created_on = models.DateTimeField(auto_created=True)
    name = models.TextField()
​
class EventData(models.Model):
    event = models.ForeignKey(Event, on_delete=models.CASCADE)
    start = models.DateTimeField()
    revision = models.IntegerField()

```

…how can I write a Django ORM query that gives me a queryset of `EventData`s in which, for each `event_id`, only the row with the highest `revision` is selected?

So say I have a DB that looks like:

```auto
Events

id | created_on | name
---+-------------+-----------------
1 | 17 Jan 2020 | Collider powering up
2 | 20 Jan 2020 | Fermion shortage

EventData

id | event_id | start | revision
--------------+-------------+---------------------
1 | 1 | 1 Feb 2020 | 0
2 | 1 | 2 Feb 2020 | 1
3 | 2 | 25 Jan 2020 | 0
4 | 2 | 26 Jan 2020 | 1
5 | 1 | 3 Mar 2020 | 2

```

the query should result in selecting the `EventData` with IDs 4 and 5.

Any help gratefully appreciated 🙂 I feel like this should be pretty simple but I can’t figure it out myself.

---

<div class="post-metadata">

**Author:** ![cmackenziek](https://sea2.discourse-cdn.com/flex026/user_avatar/forum.djangoproject.com/cmackenziek/32/307_2.png) [@cmackenziek](https://forum.djangoproject.com/u/cmackenziek)\
**Post date:** [February 10, 2020, 7:32pm UTC](https://forum.djangoproject.com/t/help-crafting-django-ormese/1123/2 "2020-02-10T19:32:24Z")

</div>

Not sure if this is the most efficient, but something like:

```
EventData.objects.order_by('event', '-revision').distinct('event')

```

I’m pretty sure if you pass a field name to distinct(), it will only evaluate that field for uniqueness. You’ll end up with the first EventData for each event with the highest revision (because of the ordering).

You could also use a Subquery to annotate EventData with the Max(‘revision’) for each event\_id and then filter for the ones where revision equals that value.