How to do SELECT MAX in Django

Question

I have a list of objects how can I run a query to give the max value of a field   I m using this code   def get best argument self       try          arg   self argument set order by  -rating   0  details     except IndexError          return  no posts      return arg   rating is an integer

User · Answer

I ve tested this for my project  it finds the max min in O n  time   from django db models import Max    Find the maximum value of the rating and then get the record with that rating     Notice the double underscores in rating  max max rating   App objects aggregate Max  rating     rating  max   return App objects get rating max rating    This is guaranteed to get you one of the maximum elements efficiently  rather than sorting the whole table and getting the top  around O n logn

User · Answer

See this  Your code would be something like the following   from django db models import Max   Generates a  SELECT MAX     query Argument objects aggregate Max  rating        rating  max   5    You can also use this on existing querysets   from django db models import Max args   Argument objects filter name  foo     or whatever arbitrary queryset args aggregate Max  rating        rating  max   5    If you need the model instance that contains this max value  then the code you posted is probably the best way to do it   arg   args order by  -rating   0    Note that this will error if the queryset is empty  i e  if no arguments match the query  because the  0  part will raise an IndexError   If you want to avoid that behavior and instead simply return None in that case  use  first     arg   args order by  -rating   first     may return None

User · Answer

Django also has the  latest field name   None   function that finds the latest  max  value  entry  It not only works with date fields but also with strings and integers   You can give the field name when calling that function   max rated entry   YourModel objects latest  rating   return max rated entry details   Or you can already give that field name in your models meta data   from django db import models  class YourModel models Model        your class definition     class Meta          get latest by    rating    Now you can call  latest    without any parameters   max rated entry   YourModel objects latest   return max rated entry details

[django] How to do SELECT MAX in Django?

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