Python 在过滤器 SQLAlchemy 中进行日期时间比较
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Doing DateTime Comparisons in Filter SQLAlchemy
提问by user1431282
I'm a bit confused about filtering in SQLAlchemy.
我对 SQLAlchemy 中的过滤有点困惑。
I currently am trying to filter out entries greater than 10 weeks, so I have
我目前正在尝试过滤掉超过 10 周的条目，所以我有
current_time = datetime.datetime.utcnow()
potential = session.query(Subject).filter(Subject.time < current_time - datetime.timedelta(weeks=10))
However, the potential.count()always returns 0.
但是，potential.count()总是返回0。
My theory is that I am not using the filter statement correctly because when I try to use a column that is not of type Column(DateTime())but instead
我的理论是我没有正确使用过滤器语句，因为当我尝试使用不是类型的列Column(DateTime())而是
Column(String(250))
列（字符串（250））
like
喜欢
potential = session.query(Subject).filter(Subject.string_field < current_time - datetime.timedelta(weeks=10))
SQLAlchemy will still not complain.
SQLAlchemy 仍然不会抱怨。
Also, when I do a manual check with
另外，当我进行手动检查时
curr_time - session.query(Subject).first().time > datetime.timedelta(weeks=10)
I get Truewhich implies that the count should not be 0.
我明白True这意味着计数不应该是0.
Am I missing something obvious? Any help would be appreciated.
我错过了一些明显的东西吗？任何帮助，将不胜感激。
采纳答案by Ian Wilson
If you switch the <to a >you can get all subjects within the last ten weeks:
如果您切换<到 a>您可以在过去十周内获得所有科目：
current_time = datetime.datetime.utcnow()
ten_weeks_ago = current_time - datetime.timedelta(weeks=10)
subjects_within_the_last_ten_weeks = session.query(Subject).filter(
Subject.time > ten_weeks_ago).all()
Filter generates a WHEREclause which includesresults matching the clause. So the results are not "filtered out" but are included.
过滤器生成一个WHERE子句，其中包含与该子句匹配的结果。所以结果没有被“过滤掉”，而是被包括在内。
