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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