django/python: raw sql with multiple tables

I need to perform a raw sql on multiple tables. I then render the result set. For one table I would do:

sql = "select * from my_table"
results = my_table.objects.raw(sql)

For multiple tables I am doing:

sql = "select * from my_table, my_other_table where ...."
results = big_model.objects.raw(sql)

But, do I really need to create a table/model/class big_model, which contains all fields that I may need? I will never actually store any data in this "table".

ADDED:

I have a table my_users. I have a table my_listings. These are defined in Models.py. The table my_listings has a foreign key to my_users, indicating who created the listing.

The SQL is

"select user_name, listing_text from my_listings, my_users开发者_如何学编程 where my_users.id = my_listings.my_user_id". 

I want this SQL to generate a result set that I can use to render my page in django.

The question is: Do I have to create a model that contains the fields user_name and listing_text? Or is there some better way that still uses raw SQL (select, from, where)? Of course, my actual queries are more complicated than this example. (The models that I define in models.py become actual tables in the database hence the use of the model/table term. Not sure how else to refer to them, sorry.) I use raw sql because I found that python table references only work with simple data models.

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1. This works. Don't know why it didn't before :( From Dennis Baker's comment:

You do NOT need to have a model with all the fields in it, you just need the first model and fields from that. You do need to have the fields with unique names and as far as I know you should use "tablename.field as fieldname" to make sure you have all unique fields. I've done some fairly complex queries with 5+ tables this way and always tie them back to a single model. –

2 . Another solution is to use a cursor. However, a cursor has to be changed from a list of tuples to a list of dictionaries. I'm sure there are cleaner ways using iterators, but this function works. It takes a string, which is the raw sql query, and returns a list which can be rendered and used in a template.

from django.db import connection, transaction

def sql_select(sql):
    cursor = connection.cursor()
    cursor.execute(sql)
    results = cursor.fetchall()
    list = []
    i = 0
    for row in results:
        dict = {} 
        field = 0
        while True:
           try:
                dict[cursor.description[field][0]] = str(results[i][field])
                field = field +1
            except IndexError as e:
                break
        i = i + 1
        list.append(dict) 
    return list  

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you do not need a model that includes the fields that you want to return from your raw sql. If you happen to have a model that actually has the fields that you want to return from your raw sql then you can map your raw sql output to this model, otherwise you can use cursors to go around models altogether.