Question

我想从关联表中删除行，这是对表组的辅助表。

class Groups(db.Model):
    __tablename__ = 'groups'

    group_id = db.Column(db.Integer(), Sequence('groups_id_seq') , primary_key=True)
    group_name = db.Column(db.String())
    group_desc = db.Column(db.String())
    ngo_id = db.Column(db.String(), db.ForeignKey('ngo.ngo_id'))
    delete = db.Column(db.Boolean())

    group_donors = db.relationship('Donor', secondary=groups_donor_table, backref='groups')

    def __init__(self, group_name=None, group_desc=None, ngo_id=None, delete=True):
        self.group_name = group_name
        self.group_desc = group_desc
        self.ngo_id = ngo_id
        self.delete=delete

关联表

groups_donor_table=db.Table('groups_donor_table',
                    db.Column('group_id', db.Integer, db.ForeignKey('groups.group_id'), nullable=False),
                    db.Column('donor_id', db.Integer, db.ForeignKey('donor.id'), nullable=False),
                    db.PrimaryKeyConstraint('group_id', 'donor_id')
                )

删除行的代码

def delete_group_donors(group_id, json):
    donor_ids = json['delete_donors']
    group = db.session.query(Groups).filter_by(group_id=group_id).first()
    for donor_id in donor_ids:
     group_donor=db.session.query(groups_donor_table).filter_by(group_id=group_id, donor_id=donor_id).first()
        print group_donor
        group.group_donors.remove(group_donor)
        db.session.commit()

我能够检索数据并添加到表中，但不能删除行。

错误----

File "/home/mayur/Desktop/sahaj-backend/app.py", line 393, in update_group delete=delete_group_donors(group_id, details) File "/home/mayur/Desktop/sahaj-backend/app.py", line 432, in delete_group_donors group.group_donors.remove(group_donor) File "/home/mayur/.local/lib/python2.7/site-packages/sqlalchemy/o‌rm/collections.py", line 1054, in remove fn(self, value) ValueError: list.remove(x): x not in list

Answer 1

您尝试删除的内容是(group_id, donor_id)元组。您根本无需手动操作groups_donor_table因为关系group_donors已经为您处理了它。您需要从group_donors中删除的内容不是(group_id, donor_id)元组，而是Donor实例，id等于donor_id。

更直接的方法是简单地建立一个应该保留的新捐赠者名单：

donor_ids_set = set(donor_ids)
group.group_donors = [donor for donor in group.group_donors if donor.id not in donor_ids_set]

使用SQLAlchemy从postgress关联表中删除元组

1 个答案: