Mongo db query return partial contents of a field based on a condition

Question

I'm just wondering if it's possible to run a query to grab only a partial of a certain field based on a condition. For example my data set looks like:

"Name":"John",
"History":[ 
    {
        "speed" : 5,
        "type" : "walking"
    }, 
    {
        "speed" : 6,
        "type" : "walking"
    }, 
    {
        "speed" : 7,
        "type" : "walking"
    }
]

I want to run a query like:

db.getCollection('membermodel').find({
    "Name":"John"
}, {
    "Name":"1",
    "History":"1",
    //specify field condition here 
    "History.speed":{$gt:6}
});

will give me a result only containing the data which its speed is greater than 6:

"Name":"John",
"History":[ 
    {
        "speed" : 7,
        "type" : "walking"
    }
]

Thank you very much in advance. Mars

great! Can you please let me know which commend shall I use? I've been reading the documentation for a few hours now:( Thank you! — Mars Zhu, Sep 09 '15 at 08:29
You have the gt in the wrong place. Should be something like - "Name":"John", History : {$eleMatch : speed..... — gpullen, Sep 09 '15 at 08:29
possible duplicate of [Retrieve only the queried element in an object array in MongoDB collection](http://stackoverflow.com/questions/3985214/retrieve-only-the-queried-element-in-an-object-array-in-mongodb-collection). See the `$elemMatch` or positional `$` examples for a single match and the `.aggregate()` examples for multiple matches. — Blakes Seven, Sep 09 '15 at 08:41
@gpullen Thank you for your reply. That still return the full History array, I just want to return a partial set of "History" — Mars Zhu, Sep 09 '15 at 08:45

score 3 · Answer 1 · edited May 14 '21 at 21:33

3

db.getCollection('test').find({"Name":"John"},{"Name":1, "History":{$elemMatch :{"speed":{$gt:6}}}});

The $elemMatch operator matches documents that contain an array field with at least one element that matches all the specified query criteria.

edited May 14 '21 at 21:33

elp

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answered Sep 09 '15 at 11:26

TharunRaja

707
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score 0 · Answer 2 · answered Sep 09 '15 at 08:49

0

For partial result use below query:

db.getCollection('test').find({"History.speed":7},{_id: 0, 'History.type.$': 1})

This will give only those History objects which will pass your criterion.

answered Sep 09 '15 at 08:49

Abie

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Criteria looks wrong here as compared to the question asked by the OP as this will only match things where the value is "exactly" 7. Also there is a marked duplicate here long before your reply, which contains only "one" of the many possible answers listed there. – Blakes Seven Sep 09 '15 at 09:11

Mongo db query return partial contents of a field based on a condition

2 Answers2