我正在利用KallAlchemy建立一个地图集网。 我怎么能够检查一下是否存在某些数据,是否存在着真实和反面的数据?
你可以做这样的事情:
exists = db.session.query (your_id).filter_by(your_filter).scalar()不是。
或者你可以这样做:
def check_exists():
return True if session.query(data).filter().one() else False
我们能够做到:
exist_query = db.session.query(model).filter_by(column = some_val).exists()
if db.session.query(exist_query).scalar():
# implement logic here
Note:
The db.session.query(exist_query).scalar() gives the boolean value while the exist_query is a query object .
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