To make it work I selected a column for the primary key as you suggested, and that worked thanks. However, my selection of a primary_key column could be arbitrary as there is no real primary key in my SELECT statement.
When defining a table, I can define a foreign key column. Then when creating the mapper, I define a relation(). This allows my object to have an attribute that actually references an object, and all is good. I am able to query my objects based on criteria for their children objects like so: class Shipment - date - job (Job object) query(Shipment).filter(Job.number==12345).all() ... gets me all shipments where the job number is 12345 When using a select statement in my mapper instead of a table, how do I tell SA that a certain field in the SELECT is a foreign key? Is it possible to set up a relation in a mapper that is based on a SELECT statement. When I did it, it seemed to join my SELECT statement with the job table as a Cartesian product, because it didn't understand how to join my SELECT statement with the job table because there were no foreign keys defined. On Sep 14, 3:00 pm, "Michael Bayer" <mike...@zzzcomputing.com> wrote: > Bryan wrote: > > > I want to abstract some ugly reporting SQL strings into a read-only > > object model. I have created an empty class, and then I map it to a > > select object that pulls some statistical information from the DB. > > The mapper is complaining that it can't assemble a primary key. I am > > only using this object as a simplified way of querying the database, > > and will never want to persist the object. The object is read-only. > > Is there a way to tell sqlalchemy not to worry about persisting this > > class? > > the primary key is for more than just persistence. Pick whatever columns > on your select object you think are suitable, then configure them on the > mapper using the "primary_key" option: > > mapper(MyClass, myselect, primary_key=[myselect.c.foo, myselect.c.bar]) --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalchemy@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 -~----------~----~----~----~------~----~------~--~---
