On Apr 2, 2008, at 1:28 PM, Bobby Impollonia wrote:
>
> Hi. I have a simple model that looks like this:
> Base = declarative_base(metadata=metadata)
>
> class Item(Base):
> __tablename__ = 'item'
> id = Column('id', Integer, primary_key=True)
> group = Column('group', Integer)
>
> Groups have no useful information other than the items they contain,
> so I don't have a group table and the group column is not a foreign
> key. The group column exists just to group associated Items.
>
> I have a query that starts like this:
> i2 = Item.__table__.alias() # Item.alias() doesn't work :(
> session.query(Item).join(i2, i2.c.group == Item.c.group)...
> , but it fails on the join saying:
> <class 'sqlalchemy.exceptions.InvalidRequestError'>: Mapper
> 'Mapper|Item|item' has no property ''
> Why does my mapper need a connection between Item and Item if I am
> specifying in the join the condition to use? I'm not even sure how I
> would specify that relation. How do I make this join work?
> Thanks.
>
query.join() is only intended for relations(). To join on tables
directly use query.select_from(table1.join(table2,
onclause)).filter(..)...etc.
- mike
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