列中的最后一条记录，SQLALCHEMY

Question

我试图使用这个获取我专栏中的最后一条记录

 ObjectRes.query.order_by('-id').first()

但结果是：无

我尝试使用所有其他查询，唯一有效的是

obj = ObjectRes.query.all()
return str(obj[-1].id)

查询太繁重，需要在 Pythonanywhere 上使用更轻量级的查询。谢谢

Answer 1

Columns in SQLAlchemy models have methods attached to produce this behaviour. To order by ID descending, do this:

descending = Object.query.order_by(Object.id.desc())
last_item = descending.first()

Specifying Object.field is the clearest syntax for choosing a field to order by, and all columns / model attributes should support .desc() or .asc()

You can of course do this in a one liner as well:

last_item = Object.query.order_by(Object.id.desc()).first()