Python SqlAlchemy order_by DateTime?

Question

I'm using SqlAlchemy to store some objects with a DateTime field:

my_date = Field(DateTime())

I'd like to run a query to retrieve the most recent few objects (Entities with the my_date field that are the most recent).

I've tried the following:

entities = MyEntity.query.order_by(MyEntity.time).limit(3).all()
entities = MyEntity.query.order_by(-MyEntity.time).limit(3).all()

But these queries return the same objects in the same order. The SqlAlchemy documentation notes the use of the '-' to reverse the order, but I'm surely missing something here.

Can anyone help?

Answer 1

You can do it like this:

entities = MyEntity.query.order_by(desc(MyEntity.time)).limit(3).all()

You might need to:

from sqlalchemy import desc

Here's some documentation.

Another option is this:

stmt = select([users_table]).order_by(users_table.c.name.desc())

Answer 2

entities = MyEntity.query.order_by(MyEntity.my_date.desc()).limit(3).all()

should work.

Answer 3

You can use like this

from sqlalchemy import desc

db.session.query(MyEntity).order_by(desc(MyEntity.time))