#8634: Wrong ordering by a field in a different table example in new
(development
) queryset-api documentation
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Reporter: [EMAIL PROTECTED] | Owner: nobody
Status: new | Milestone:
Component: Documentation | Version: SVN
Keywords: | Stage: Unreviewed
Has_patch: 0 |
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The example on ordering a queryset by a field in a different table in the
'''development''' documentation on queryset-api
([http://docs.djangoproject.com/en/dev/ref/models/querysets/#queryset-
api]) offers the following syntax:
{{{
Entry.objects.order_by('blogs_blog.name', 'headline')
}}}
preceded by the following explanation: "To order by a field in a different
table, add the other table’s name and a dot, like so:"
For the following model definitions
{{{
from django.db import models
class Poll(models.Model):
question = models.CharField(max_length=200)
pub_date = models.DateTimeField('date published')
def __unicode__(self):
return self.question
class Choice(models.Model):
poll = models.ForeignKey(Poll)
choices = models.CharField(max_length=200)
votes = models.IntegerField()
def __unicode__(self):
return self.choices
}}}
with MySQL, for this retrieval example:
{{{
c=Choice.objects.order_by("polls_poll.question",'-votes')
list(c)
}}}
the result is "OperationalError: (1054, "Unknown column
'polls_poll.question' in 'order clause'" in reply to the following SQL
query generated:
{{{
SELECT `polls_choice`.`id`, `polls_choice`.`poll_id`,
`polls_choice`.`choices`,
`polls_choice`.`votes` FROM `polls_choice` ORDER BY `polls_poll`.question
ASC,
`polls_choice`.`votes` DESC
}}}
On the other hand
if one follows the syntax offered in the "mainstream" documentation
(http://www.djandoproject.com/db-api), i.e.,
{{{
c=Choice.objects.order_by("poll__question",'-votes')
list(c)
}}}
things do work, with the following SQL query generated:
{{{
SELECT `polls_choice`.`id`, `polls_choice`.`poll_id`,
`polls_choice`.`choices`,
`polls_choice`.`votes` FROM `polls_choice` INNER JOIN `polls_poll`
ON (`polls_choice`.`poll_id` = `polls_poll`.`id`) ORDER BY
`polls_poll`.`question` ASC,
`polls_choice`.`votes` DESC
}}}
This problem might be related to the one reported in the accepted ticket
#2884 (component: Admin interface), solution for which is said to be
deferred until after queryset-refactor.
--
Ticket URL: <http://code.djangoproject.com/ticket/8634>
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