db['Copy(1)_of_20180401'].find({'t':{$gte:'2018-04-01 20:00:00'},'t':{$lte:'2018-04-01 21:00:00'}})
db['Copy(1)_of_20180401'].remove({'t':{$not:{$lte:'2018-04-01 22:00:00'}}})
db['Copy(1)_of_20180401'].aggregate({"$group":{_id: 'avg',avg_value:{"$avg":"$uf"}}});
這篇文章寫的很全面:https://blog.csdn.net/zwq9123....net