SQLAlchemy ORM：选择具有多个 JOIN 和 WHERE 子句的特定列

Question

I'm trying to find a more pythonic way of executing SQL queries using the SQLalchemy ORM. Below is a sample SQL statement:

SELECT A.payment_plan_id, A.plan_id, A.amount, C.promo_code, B.sso_guid, B.user_id
FROM payment_plans as A
JOIN users as B ON A.user_id = B.user_id
JOIN invoices as C ON A.invoice_id = C.invoice_id
WHERE A.due_date::date < '01/01/2022'::date
AND (A.status = 'pending' OR A.status = 'failed')

Tried this approach:

orm_query = session.query(
    select(
        payment_plans.payment_plan_id,
        payment_plans.plan_id,
        payment_plans.amount,
        invoices.promo_code,
        users.sso_guid,
        users.user_id,
   )
   .join(users, payment_plans.user_id == users.user_id)
   .join(invoices, payment_plans.invoice_id == invoices.invoice_id)
   .where(payment_plans.due_date < '01/01/2022')
   .where(payment_plans.status in ["pending", "failed"])
)

and I'm always ending up with this error:

sqlalchemy.exc.ArgumentError: Column expression or FROM clause expected, got <sqlalchemy.sql.selectable.Select object at 0x7fe342d7ca60>. To create a FROM clause from a <class 'sqlalchemy.sql.selectable.Select'> object, use the .subquery() method.

I'm not sure what it means and I scoured google looking for answers. Any help is appreciated. Thanks!

Answer 1

session.query and select both basically do the same thing, but session.query returns instances of your mapped classes while select returns rows like a traditional DB API. This means that you have to use session.query like you use select in your example and call .all() to receive a QueryResult your objects. Or you use select without the outer session.query and use your engine to execute the query. I assume that you want to use the latter:

query = select(

    payment_plans.payment_plan_id,
    payment_plans.plan_id,
    payment_plans.amount,
    invoices.promo_code,
    users.sso_guid,
    users.user_id,
)
   .join(users, payment_plans.user_id == users.user_id)
   .join(invoices, payment_plans.invoice_id == invoices.invoice_id)
   .where(payment_plans.due_date < '01/01/2022')
   .where(payment_plans.status in ["pending", "failed"])

result = engine.execute(query)

TIP: Install sqlalchemy-stubs (the official type stubs for sqlalchemy) via pip to get API hints for sqlalchemy in your IDE and a better feeling for what works and what not (works with VSCODE at least; you may have to restart your IDE).

Answer 2

I managed to make this work by not using select , and notice the use of in_ for value evaluation with a list.

 orm_query = (
    session.query(
        payment_plans.payment_plan_id,
        payment_plans.plan_id,
        payment_plans.amount,
        invoices.promo_code,
        users.sso_guid,
        users.user_id,
   )
   .join(users, payment_plans.user_id == users.user_id)
   .join(invoices, payment_plans.invoice_id == invoices.invoice_id)
   .where(payment_plans.due_date < '01/01/2022')
   .where(payment_plans.status.in_(["pending", "failed"]))
)