You are actually right. There was a logical mistake in my request, so I
have to rephrase it:
Having a table Assets with columns category (String) and created
(DateTime), I would like to get the newest n records for each category.
On 10/11/2010 04:30 PM, Mark Erbaugh wrote:
On Oct 11, 2010, at 7:50 AM, Sebastian Elsner wrote:
have one table called 'Assets' with a 'category' (String) and
'created' (DateTime) column. Now I would like to find the records
created since a given datetime for each category:
This is what I thought would work (with a self-join):
session.query(Asset).join(Asset, and_(Asset.category ==
Asset.category, Asset.created > specifiedDateTime)
But it does error with 'Cant find any foreign key relationships...'
How can I fix this? Or do you have a better idea how to accomplish the
task?
You probably don't need the self join? You can filter on multiple
conditions.
session.query(Asset).filter(Asset.category ==
spefiiedCateogory).filter(Asset.created > specifiedDateTime)
or the equivalent using the and_ function
session.query(Asset).filter(and_(Asset.category == specifiedCategory,
Asset.created > specifiedDateTime))
Mark
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