Primary key requirement in raw SQL complicates the query in Django

Question

To get max value from a simple table of values, I can write the following query in Django:

MyTable.objects.aggregate(Max(\'value\'))

The SQ

Answer 1

U can use

ModelName.objects.raw('SELECT 1 as id , max(value) FROM mytable')

Answer 2

You should use custom SQL instead of Manager.raw() method:

from django.db import connection

cursor = connection.cursor()
cursor.execute('SELECT max(value) FROM mytable')
max_value = cursor.fetchone()[0]

Answer 3

I would do something like:

select id, value from mytable order by value desc limit 1

Answer 4

I just had same issue, @Tinashe Robert's not working for me. May I share my solution(Python 3.7.7, Django 3.0.5):

PS: Yes, @catavaran's answer is native Python, but if one really want to use RAW?

• Firstly, primary_key needs to be appointed to one column in MySQL DB field, i.e.:

 class MyTable(model.Model):
     id = models.AutoField(primary_key=True)
     value = models.IntegerField(10)
     ... 

with API shell:

>>> MyTable.objects.raw('SELECT id, max(value) as mx from MyTable')[0].mx

or simpler solution:

>>> from django.db.models import Max
>>> MyTable.objects.all().aggregate(Max('value'))