Re: Django help required with non foreign key relations

Ohh this looks little promising..

However,

1. I need a few cols of table1 and few from table 2 to be displayed. How can we achieve that at the .filter() level? and 
2. At the view level like using the list_display () for displaying them in the Admin interface

On Sunday, 22 April 2012 21:30:41 UTC+5:30, akaariai wrote:

On Apr 22, 1:31 pm, Aditya Sriram M <aditya.cr3...@gmail.com> wrote:
> File myapp/models.py has this sample code..
>
> from django.db import models
>
> # model for 'user' table in database oracle_dbuser1:user
> class User(models.Model):
>     . . .
>     customerid = models.BigIntegerField()
>
> # model for 'customer' table in database oracle_dbuser2:customer
> # Note that there is no Foreign key integrity among these legacy tables.
> class Customer(models.Model):
>     . . .
>     customerid = models.BigIntegerField()
>
> and the file myapp/admin.py has the following code:
>
> from maasusers.models import User, Customer
> from django.contrib import admin
>
> class UserAdmin(admin.ModelAdmin):
>     # A handy constant for the name of the alternate database.
>     db_one = 'dbuser1'
>     db_two = 'dbuser2'
>
>     # display in a list
>     list_display = (. . .) # question 1
>
>     def queryset(self, request):
>         result = super(UserAdmin, self).queryset(request).using(self.db_one) # question 2
>         return result
>
> # Register the Poll class
> admin.site.register(User, UserAdmin)
> admin.site.register(Customer, UserAdmin)
>
> Question 1: Refer above: I want to display columns of both the tables. How
> can I achieve this? Eg.Select usr.col1, usr.col2, cust.col1, cust.col10
> from user usr, customer cust where usr.col2 = cust.col3;
>
> Question 2: How to write a corresponding queryset() function using the using
>  function?

There is no way to do a join between models if there is no relation
between them. I see two ways forward: modify one of the models to have
a foreign key - even if there is no foreign key in the DB, you can
have one in the models - or do the join in Python (fetch all
customers, then fetch users by
User.objects.filter(customerid__in=[obj.customerid for obj in
customers]). Finally join users to its customer).

 - Anssi

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