you're using homologues to link Protein_seed to PDB. so the two
foreign keys should be between the tables named "Proteins_seed" and
"PDB", not "Proteins_putative", which seems to be otherwise
unmentioned here.
On Feb 1, 2009, at 11:57 AM, Piotrek Byzia wrote:
>
> Hi,
>
> I'm a fresh user of SQLA, and this is my first attempt to use it.
>
> Based on the official tutorial example I created a many to many
> relation between two tables, but I have some issues with getting it
> working. It returns error "Could not determine join condition between
> parent/child tables on relation Protein_seed.pdb_entry. Specify a
> 'primaryjoin' expression. If this is a many-to-many relation,
> 'secondaryjoin' is needed as well." I don't know how to define
> secondary key, while my association table "homologues" is not
> declarative and doesn't have it's own primary key. Can anybody help,
> please?
>
> meta = MetaData()
> Base = declarative_base(metadata=meta)
>
> homologues = Table('Homologues', meta,
> Column('protein_seed_id', Integer, ForeignKey
> ('Proteins_seed.id')),
> Column('protein_putative_id', Integer, ForeignKey
> ('Proteins_putative.id'))
> )
>
> class PDB(Base):
> __tablename__ = 'PDB'
>
> id = Column(Integer, primary_key=True)
> name = Column(String, nullable=False, unique=True)
> chain = Column(String, nullable=False)
>
> def __init__(self, name, chain):
> self.name = name
> self.chain = chain
>
> def __repr__(self):
> return "<PDB('%s', '%s')>" % (self.name, self.chain)
>
> class Protein_seed(Base):
> __tablename__ = 'Proteins_seed'
>
> id = Column(Integer, primary_key=True)
> name = Column(String, nullable=False)
> sequence = Column(String, nullable=False)
> length = Column(Integer, nullable=False)
> alignment = Column(String, nullable=False)
> pdb_id = Column(Integer, ForeignKey('PDB.id'))
>
> # many-to-one Protein_seed * 1 PDB
> pdb_entry = relation('PDB', secondary=homologues, backref=backref
> ('Proteins_seed'),
> primaryjoin=pdb_id == PDB.id)
>
> def __init__(self, name, sequence, length, alignment):
> self.name = name
> self.sequence = sequence
> self.length = length
> self.alignment = alignment
>
> def __repr__(self):
> return "<Protein_seed('%s', '%s', '%s', '%s')>" % (self.name,
> self.sequence, self.length, self.alignment)
>
>
> >
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