从加入的 table 添加列

Question

我正在使用 Python 2.7+flask-sqlalchemy。我定义了以下 models/table：

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)
)

我有以下查询：

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

我收到以下错误：

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

我做错了什么？

Answer 1

我找到了解决方案。正确的查询方式应该是：

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

从加入的 table 添加列

Adding columns from joined table

python

sqlalchemy

flask

flask-sqlalchemy