#10060: Multiple table annotation failure
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Reporter: [email protected] | Owner:
Status: new | Milestone: 1.1
Component: ORM aggregation | Version: SVN
Resolution: | Keywords:
Stage: Accepted | Has_patch: 0
Needs_docs: 0 | Needs_tests: 0
Needs_better_patch: 0 |
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Comment (by bendavis78):
If anyone were to fix this, the first question to ask would be how you
would structure the SQL. I'm not an SQL efficiency expert, but I know
one way to get the correct result would be to use subqueries in the SELECT
clause:
For example, let's say I have a User, !PointEarning w/
!ForeignKey(User), and !PointExpense w/ F!oreignKey(User). Let's say I
want a query to get the user's email, total points earned, and total
points spent.:
{{{
SELECT auth_user.id, auth_user.email, (SELECT SUM(points) FROM
app_pointearning WHERE user_id=auth_user.id) AS points_earned, (SELECT
SUM(points) FROM app_pointexpense WHERE user_id=auth_user.id) AS
points_spent FROM auth_user
}}}
Another way, I believe, is to join on derived tables (sub-queries).
Whatever way we decide to write the SQL, django could perhaps detect when
we're using aggregates accross multiple joins, and alter the structure of
the query accordingly. Seems like it could be kinda messy, but at least
the results would be more what the user expected.
--
Ticket URL: <http://code.djangoproject.com/ticket/10060#comment:7>
Django <http://code.djangoproject.com/>
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