Asked By – user1105851
I don’t have much experience with SQLAlchemy and I have a problem, which I can’t solve. I tried searching and I tried a lot of code.
This is my Class (reduced to the most significant code):
class Patient(Base): __tablename__ = 'patients' id = Column(Integer, primary_key=True, nullable=False) mother_id = Column(Integer, ForeignKey('patients.id'), index=True) mother = relationship('Patient', primaryjoin='Patient.id==Patient.mother_id', remote_side='Patient.id', uselist=False) phenoscore = Column(Float)
and I would like to query all patients, whose mother’s phenoscore is (for example)
As told, I tried a lot of code, but I don’t get it. The logically solution, in my eyes, would be
patients = Patient.query.filter(Patient.mother.phenoscore == 10)
because, you can access
.mother.phenoscore for each element when outputting but, this code doesn’t do it.
Is there a (direct) possibility to filter by an attribute of a relationship (without writing the SQL Statement, or an extra join-statement), I need this kind of filter more than one time.
Even if there is no easy solution, I am happy to get all answers.
Now we will see solution for issue: SqlAlchemy – Filtering by Relationship Attribute
has() of relationship (more readable):
patients = Patient.query.filter(Patient.mother.has(phenoscore=10))
or join (usually faster):
patients = Patient.query.join(Patient.mother, aliased=True)\ .filter_by(phenoscore=10)
This question is answered By – Denis Otkidach
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