[sqlalchemy] Newest records per category
Hello, I 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? Thank you, Sebastian -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
Re: [sqlalchemy] Newest records per category
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 -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
Re: [sqlalchemy] Newest records per category
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 -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en. -- Sebastian Elsner - Pipeline TD - r i s e | fx t: +49 30 201 803 00 sebast...@risefx.com c: +49 175 336 5739 7548 www.risefx.com r i s e | fx GmbH Schlesische Strasse 28, Aufgang B 10997 Berlin Richard-Byrd-Strasse 12, 50829 Cologne Geschaeftsfuehrer: Sven Pannicke, Robert Pinnow Handelsregister Berlin HRB 106667 B -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
