Difference between running a SQLAlchemy query in Flask using database configuration or model? [duplicate]

Question

Say I have a model in my Flask application like this:

class Foo(db.Model):
     id = db.Column(db.Integer, primary_key=True)
     bar = db.Column(db.String)

In a Flask view, I want to query my database to retrieve a record of this type.

In tutorials I've seen people run such a query in two ways: using the flask.ext.sqlalchemy.SQLAlchemy configuration or the model.

Using `flask.ext.sqlalchemy.SQLAlchemy`

The app is set up something like this ...

from flask import Flask
from flask.ext.sqlalchemy import SQLAlchemy

app = Flask(__name__)
app.config.from_object(os.environ['MY_SETTINGS'])
db = SQLAlchemy(app)

Then the query in the view looks like this ...

my_query = db.session.query(Foo).filter_by(id=some_id)

Using the model

The other way I've seen the query executed is using the model, like this ...

import Foo
my_query = Foo.query.filter_by(id=some_id)

What's the difference?

As far as I can tell, the query returns exactly the same thing. So it's hard for me to tell which method I should be using. Or does it make no difference?

What about when it comes to creating and deleting records?

freethebees · Accepted Answer · 2016-03-24 15:54:52Z

1

It's exactly the same thing, but coming from two different approaches.

The classic SQLAlchemy approach is db.session.query(Foo).filter_by(id=some_id).

Then Flask-SQLAlchemy, among other things, add a property to all models to enable the second approach Foo.query.filter_by(id=some_id).

Additional context (if needed): the second approach mimics the one Django ORM is using, but if you look for SQLAlchemy material on the web you'll mostly find the first approach.

edited Mar 24, 2016 at 15:54

freethebees

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answered Mar 24, 2016 at 13:19

b4stien

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1 Comment

freethebees Over a year ago

Thanks @b4stien. I did wonder whether they might just the same thing and down to preference. It makes sense that they might mimic the Django ORM. It's a shame none of the early-stage tutorials I've seen have mentioned this quirk.

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Difference between running a SQLAlchemy query in Flask using database configuration or model? [duplicate]

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