how to delete a specific row from a table sqlalchemy with flask?

Question

i want to delete specific row in a db.table i have these code

num_rows_deleted=db.session.query(Orders).filter(Orders.c.id==id).first()
db.session.delete(num_rows_deleted)
db.session.commit()

Orders = db.Table('orders', db.Model.metadata,
            db.Column('id', db.Integer,primary_key=True),
              db.Column('user_id', db.Integer, db.ForeignKey('user.id')),
              db.Column('book_id', db.Integer, db.ForeignKey('books.id')),
              db.Column('quantity', db.Integer,default=1, nullable=False),
              db.Column('created_at',db.DateTime, default=datetime.datetime.now),
            db.Column('updated_at',db.DateTime, onupdate=datetime.datetime.now))

these is the table

but i get these error and i dont know how to fix it sqlalchemy.orm.exc.UnmappedInstanceError: Class 'sqlalchemy.util._collections.result' is not mapped

Hi Wael, please show us the output as you get it in your python terminal, this will help people identify the issue. Also writing a toy problem that's shows your issue can help in resolving the issue faster. — sukhbinder, Nov 05 '20 at 05:51
hi, these is the error that i get sqlalchemy.orm.exc.UnmappedInstanceError: Class 'sqlalchemy.util._collections.result' is not mapped — wael dagash, Nov 05 '20 at 08:20
Does this answer your question? [How to delete a record by id in Flask-SQLAlchemy](https://stackoverflow.com/questions/27158573/how-to-delete-a-record-by-id-in-flask-sqlalchemy) — Ruben Helsloot, Nov 05 '20 at 11:56

score 0 · Answer 1 · answered Nov 04 '20 at 22:23

0

Try the following instead, not fetching the value, but deleting it immediately, using Query.delete:

db.session.query(Orders).filter(Orders.c.id==id).delete()
db.session.commit()

answered Nov 04 '20 at 22:23

Ruben Helsloot

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thank you for ur answer , i get the same problem AttributeError: 'NoneType' object has no attribute 'class_' – wael dagash Nov 05 '20 at 08:18
What is the value of `id`? Is it a number or something else? – Ruben Helsloot Nov 05 '20 at 09:44
yes its a number - and itis the primary key of the order table. these the whole function from the views.py @app.route('/delete_order/',methods=["GET", "POST"]) @flask_login.login_required def delete_order(id): row_to_delete = db.session.query(Orders).filter(Orders.c.id == id).delete() db.session.delete(row_to_delete) db.session.commit() – wael dagash Nov 05 '20 at 11:29
Remove the `db.session.delete(row_to_delete)` part, just leave exactly what I wrote – Ruben Helsloot Nov 05 '20 at 11:45
1

still the same thing AttributeError: 'NoneType' object has no attribute 'class_' – wael dagash Nov 05 '20 at 11:54

score 0 · Answer 2 · answered Nov 05 '20 at 04:03

0

You can try this

row_to_delete = db.session.query(Orders).filter(Orders.id==id).one()
db.session.delete(row_to_delete)
db.session.commit()

answered Nov 05 '20 at 04:03

Mohammad Aarif

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i try to use these code but i get AttributeError: 'Table' object has no attribute 'id' – wael dagash Nov 05 '20 at 08:19

score 0 · Accepted Answer · answered Nov 06 '20 at 18:17

thank you all - i used Deleting Rows from the Many to Many Table¶ from these site https://docs.sqlalchemy.org/en/13/orm/basic_relationships.html

my table is a seconday table and it is connected to two tables , so i used remove to delete , and append to add .

how to delete a specific row from a table sqlalchemy with flask?

3 Answers3