django select max field from mysql when column is varchar

Using Django 1.1, I am trying to select the maximum value from a varchar column (in MySQL.) The data stored in the column looks like:

9001

9002

9017

9624

10104

11823

(In reality, the numbers are much bigger than this.)

This worked until the numbers incremented above 10000:

Feedback.objects.filter(est__pk=est_id).aggregate(sid=Max('sid'))

Now, that same line would return 9624 instead of 11823.

I'm able to run a query directly in the DB that gives me what I need, but I can't fi开发者_StackOverflow中文版gure out the best way to do this in Django. The query would be:

select max(sid+0) from Feedback;

Any help would be much appreciated.

Thanks!

In the spirit of "any help would be much appreciated", you should figure out why it stopped working inside Django (but apparently not inside MySQL) - at 10,000.

What is the query that is being generated? See this question for how to find that out.

I suspect it is because you're adding the +0 to make the sort numeric in your query. I don't think Django supports this naturally, so you have two options:

• People will undoubtedly want to know why you're storing a number and asking for the maximum of it in a VARCHAR column. You could change the column to a numeric data type.
• You could do what you have to do whenever you want to make some custom SQL call and Django doesn't yet support it: write your own raw SQL.
• Edit: You could also patch Django, but this might be a MySQL specific thing, so option #2 is probably your best bet.