SQLAlchemy one-to-one, store foreign key in each table?

问题

I have a relationship that is one to one between cage codes and duns numbers.

I have set up my relationship that looks like, where I store a ForeignKey on each of the respective tables.

class Cage(Base):
    __tablename__ = 'DimCage'

    id = Column(Integer, primary_key=True)
    cage = Column(String(8), unique=True, nullable=False)
    duns_id = Column(Integer, ForeignKey('DimDuns.id'))

    duns = relationship('Duns', uselist=False, back_populates='cage')


class Duns(Base):
    __tablename__ = 'DimDuns'

    id = Column(Integer, primary_key=True)
    duns = Column(String(10), unique=True, nullable=False)
    dunsInt = Column(Integer, unique=True, nullable=False)
    cage_id = Column(Integer, ForeignKey('DimCage.id'))

    cage = relationship('Cage', uselist=False, back_populates='duns')

When I create the tables I get the below error, how to do I set up my foreign keys so I can keep a reference on both tables?

sqlalchemy.exc.AmbiguousForeignKeysError: Can't determine join between 'DimCage' and 'DimDuns'; tables have more than one foreign key constraint relationship between them. Please specify the 'onclause' of this join explicitly.

And During handling of the above exception, another exception occurred:

sqlalchemy.exc.AmbiguousForeignKeysError: Could not determine join condition between parent/child tables on relationship Cage.duns - there are multiple foreign key paths linking the tables. Specify the 'foreign_keys' argument, providing a list of those columns which should be counted as containing a foreign key reference to the parent table.

回答1:

I believe you only need to store one foreign key for a one-to-one relationship.
See https://docs.sqlalchemy.org/en/13/orm/basic_relationships.html#one-to-one

You shouldn't lose any data access this way. If you remove the duns_id column from Cage, you now access the id by cage.duns.id instead of cage.duns_id.

来源：https://stackoverflow.com/questions/56691341/sqlalchemy-one-to-one-store-foreign-key-in-each-table

标签

python

python-3.x

sqlalchemy