On Dec 4, 2012, at 2:30 PM, Diego Woitasen wrote:
> Hi,
> I have the following tables:
>
> rcpt_group_asoc = Table("mailing_rcptgroup_rcpts", Base.metadata,
> Column('rcpt_id', Integer, ForeignKey('mailing_rcpt.id')),
> Column('rcptgroup_id', Integer,
> ForeignKey('mailing_rcptgroup.id')))
>
>
> class Rcpt(Base):
> __tablename__ = 'mailing_rcpt'
>
> id = Column(Integer, primary_key=True)
>
> mail_addr = Column(String(128+256), nullable=False)
> rcpt_groups = relationship("RcptGroup", secondary=rcpt_group_asoc,
> backref="rcpts")
>
> class RcptGroup(Base):
> __tablename__ = 'mailing_rcptgroup'
>
> id = Column(Integer, primary_key=True)
> name = Column(String(64), nullable=False, unique=True)
>
> I'm trying to do:
>
>
> group = db.RcptGroup.__table__
> rcpt = db.Rcpt.__table__
> print group.join(rcpt)
>
> And got:
>
> ArgumentError: Can't find any foreign key relationships between
> 'mailing_rcptgroup' and 'mailing_rcpt'.
the join() method of Table (which is what RcptGroup.__table__ is) is part of
SQLAlchemy Core and has no awareness of the relationship() construct and
therefore no implicit awareness of the rcpt_group_assoc table, if not provided
explicitly. If using a pure Core approach, you'd need to join explicitly,
group.join(rcpt_group_assoc).join(rcpt).
Alternatively, you can use the orm.join() construct and provide the
relationship() bound attribute:
from sqlalchemy.orm import join
j = join(RcptGroup.rcpts)
though typically sticking with query.join() is the simplest approach. I never
have a need to use the standalone join() function when querying with the ORM.
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