所以我在這裏有一個相當涉及的SQL查詢。在Django中執行PostgreSQL左外連接和CASE
SELECT links_link.id, links_link.created, links_link.url, links_link.title, links_category.title, SUM(links_vote.karma_delta) AS karma, SUM(CASE WHEN links_vote.user_id = 1 THEN links_vote.karma_delta ELSE 0 END) AS user_vote
FROM links_link
LEFT OUTER JOIN auth_user ON (links_link.user_id = auth_user.id)
LEFT OUTER JOIN links_category ON (links_link.category_id = links_category.id)
LEFT OUTER JOIN links_vote ON (links_vote.link_id = links_link.id)
WHERE (links_link.id = links_vote.link_id)
GROUP BY links_link.id, links_link.created, links_link.url, links_link.title, links_category.title
ORDER BY links_link.created DESC
LIMIT 20
我所有的關係都很好(我認爲),這個查詢完美的作品,當我在我的Navicat運行PostgreSQL的,但把它變成東西Django的可以使用已經相當的挑戰。我正在使用pre-alpha 1.2開發版本(來自Subversion版本庫),所以我有來自文檔的全套工具。
這裏是我的模型笑容:
class Category (models.Model):
created = models.DateTimeField(auto_now_add = True)
modified = models.DateTimeField(auto_now = True)
title = models.CharField(max_length = 128)
def __unicode__(self):
return self.title
class Link (models.Model):
category = models.ForeignKey(Category)
user = models.ForeignKey(User)
created = models.DateTimeField(auto_now_add = True)
modified = models.DateTimeField(auto_now = True)
fame = models.PositiveIntegerField(default = 1)
url = models.URLField(max_length = 2048)
title = models.CharField(max_length = 256)
active = models.BooleanField(default = True)
def __unicode__(self):
return self.title
class Vote (models.Model):
link = models.ForeignKey(Link)
user = models.ForeignKey(User)
created = models.DateTimeField(auto_now_add = True)
modified = models.DateTimeField(auto_now = True)
karma_delta = models.SmallIntegerField(default = 1)
def __unicode__(self):
return str(self.karma_delta)
如何,我能轉
def latest(request):
links = Link.objects.all().order_by('-created')[:20]
return render_to_response('links/list.html', {'links': links})
向上述查詢?
我只能使用之類的東西取得一些進展,但如何解決我對CASE的使用超出了我的想象。任何幫助將非常感激。我總是喜歡在框架的內置ORM中工作,但是如果需要原始SQL ...
還有QuerySet.raw()進入1.2:http://simonwillison.net/static/2009/djugl-december.html – 2009-12-08 16:13:49