Please see simplified django model representation on pastebin<http://pastebin.com/c90WEyPv>
In this scheme of things, there are several SiteOffice objects that are governed by a single HeadOffice object (I haven't included either in the pastebin code). The head_office instance generates a purchase_orderindependently. A site_office generates a material_requirement and now it is up to the head_office to see whether such a purchase_order exists which has a usable PurchaseOrder.order_quantity left yet to be delivered that can be used to fulfill this material_requirement. If such a purchase_order exists, the head_office generates a delivery_order to fulfill the material_requirement. Now this means that there exist several PurchaseOrder objects that *may or may not have any corresponding* DeliveryOrder objects. I am trying to query PurchaseOrder to find instances that can fulfill a particular material_requirement.quantity. How can I use the Django ORM to find PurchaseOrder instances where PurchaseOrder.order_quantity >= Sum(DeliveryOrder.quantity) + MaterialRequirement.quantity for all DeliveryOrder instances that refer back to the PurchaseOrder. I am getting stuck as only those PurchaseOrder instances are getting returned for which at least one matching DeliveryOrder instance exists. There exist other PurchaseOrder instances for which no corresponding DeliveryOrder exists, and whose PurchaseOrder.order_quantity >= material_requirement.quantity and I would like those to be returned as well. I couldn't figure out a way to do this through the ORM, so I tried to use raw sql. But there too I'm getting stuck. Please see http://stackoverflow.com/questions/15610238 for what I have been up to. Thanks. -- You received this message because you are subscribed to the Google Groups "Django users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/django-users?hl=en. For more options, visit https://groups.google.com/groups/opt_out.
