How to use a labelled column in sqlalchemy filter?

问题

I want to use the labelled column in sqlalchemy filter. for eg:

db.session.query(
    PartMaster.name,
    PartMaster.description,
    PartTracker.actual_length,
    func.sum(PartTracker.quantity).label('quantity')
).join(PartTracker).group_by(
    PartTracker.part_master_id,PartTracker.actual_length
).all()

I need the result with quantity > 0. please advice

回答1:

In SQL if you want to filter rows by result, you need to use HAVING instructions.

So in your case:

db.session.query(
    PartMaster.name,
    PartMaster.description,
    PartTracker.actual_length,
    func.sum(PartTracker.quantity).label('quantity')
).join(PartTracker).group_by(
    PartTracker.part_master_id,PartTracker.actual_length
).having(
    func.sum(PartTracker.quantity) > 0
)

Example from doc

来源：https://stackoverflow.com/questions/34825773/how-to-use-a-labelled-column-in-sqlalchemy-filter