Adding columns from joined table

Question

I'm using Python 2.7+flask-sqlalchemy. I have the following models/table defined:

class Detail(db.Model):
    __tablename__ = 'details'
    id = db.Column(db.Integer, primary_key=True)
    ....

class Usage(db.Model):
    __tablename__ = 'details'
    id = db.Column(db.Integer, primary_key=True)
    details = db.relationship('Detail', secondary=details_usages, backref=db.backref('usages', lazy='dynamic'))
    ....

details_usages = db.Table('details_usages',
    db.Column('detail_id', db.Integer, db.ForeignKey('details.id')),
    db.Column('usage_id', db.Integer, db.ForeignKey('usages.id')),
    db.Column('is_required', db.Integer)
)

I have the following query:

models.Detail.query.join(details_usages).add_columns('details_usages.is_required').all()

I'm getting the following error:

NoSuchColumnError: "Could not locate column in row for column 'details_usages.is_required'"

What am I doing wrong?

stefanobaldo · Accepted Answer · 2015-01-16 19:56:49Z

3

I found the solution. The correct way of querying should be:

models.Detail.query.join(details_usages).add_columns(details_usages.c.is_required).all()

answered Jan 16, 2015 at 19:56

stefanobaldo

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