MongoDB:查询名称中带有空格的键 [英] MongoDB: Query a key having space in its name
问题描述
我只想从MongoDB集合中检索某些键的值.
I want to retrieve values of only certain keys from a MongoDB collection.
但是,集合中有一些键的名称带有空格",例如:
But, the collection has some keys which have a 'space' in their name like:
"Parent":{"key1": //some string,
"key2": //some string,
"key 3": //some string}
我知道这是一种错误的方法,因为理想情况下,键名中不应包含空格,但是如何查询此键?我正在使用Python和PyMongo.
I know this is a wrong approach as there shouldn't ideally be spaces in a key name but nevertheless how do I query this key? I am using Python and PyMongo.
对于普通键,我可以这样做:
For normal keys I can do this:
db.coll_name.find({"key": "India"}, {"_id": 0, "Parent.key1": 1, "Parent.key2": 1})
那么如何在上述查询的第二个参数中使用键"Parent ['key 3']"?有什么办法可以做到这一点?
So how do I use the key "Parent['key 3']" in the second argument of the above query? Is there any way to achieve this?
以下是返回数据(有效)的查询:
db.coll_name.find({}, {"Parent.key1": 1, "_id": 0})
以下是不返回数据的查询:
db.coll_name.find({}, {"Parent['key 3']": 1, "_id": 0})
推荐答案
构造此方法的唯一方法是:
Well the only way you could have constructed this is like:
content = {};
content["Parent"] = {}
content["Parent"]["key2"] = 1
content["Parent"]["key 3"] = 1
db.coll_name.insert(content)
但是您似乎想念这样做没有错:
But you seem to be missing that there is nothing wrong with doing this:
db.coll_name.find({ "Parent.key 3": 1} )
或处于投影状态
db.coll_name.find({}, { "Parent.key 3": 1 })
它是点符号" ,而不是对象符号,并且只要您引用键名(点符号是必需的),就可以了,并且可以在其中留一个空格.
It's "dot notation" and not object notation, and as long as you quote the key names ( which is mandatory for dot notation ) then all it fine and you can have a space in there.
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