mongodb查找带有数据字段的文档不存在

Question

I have mongodb document like

    {
    "_id" : ObjectId("543d563bde1e58511c264340"),
    ...some fields ...
    "pref" : [ 
        {
            "user_id" : 1,
            "value" : 0.56
        }
    ]
}

How can I find all the documents where pref does not contain an entry with user_id :1 ?

Answer 1

It's a little unclear what you're looking for here. If you want to find all entries where user_id has any other value than '1', then you'd want:

db.collection.find({"pref.user_id": {'$ne': 1}})

If you're looking for documents where the 'user_id' field doesn't exist at all:

db.collection.find({"pref.user_id": {'$exists': 0}})

Keep in mind, though the behavior of both of these queries on a nested array. What you're actually going to get is all the documents where any of the objects in the 'pref' array matches the specified condition.