how to query a mongodb using a field which is inside an array of objects

Question

I have a db object like this:

{
   "_id": ObjectID("55c247f94b0c25e5d90d0f39"),
   "districts": [
    {
        "district": "Bangalore Urban",
        "stateID": 2,
        "districtID": 1
    },
    {
        "district": "Tumkur",
        "stateID": 2,
        "districtID": 2
    }
]
}

and i have stateID with me, what mongoose query should i write to get all objects from the array districts having the stateID 2

Please help!

possible duplicate of Retrieve only the queried element in an object array in MongoDB collection. Various answers mentioning .aggregate() which is suitable for multiple matches. — Blakes Seven
– Blakes Seven, Commented Aug 6, 2015 at 9:13

Thomas Bormans · Accepted Answer · 2015-08-06 12:33:06Z

3

You will need an aggregate query. Your Mongo query will look like this:

db.collection.aggregate([{
    $unwind: 'districts'
}, {
    $match: {
        'stateID': 2
    }
}, {
    $group: {
        _id: null,
        'districts': {
        $push: '$districts'
        }
    }
}]);

$unwind creates a record from each item inside an array.

$match is your query for finding items of your stateID

$group groups all your results in a custom key districts.

edited Aug 6, 2015 at 12:33

answered Aug 6, 2015 at 10:52

Thomas Bormans

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4 Comments

Syed Faizan Over a year ago

this is returning me the full db object, no selection is happening

Thomas Bormans Over a year ago

Oh, I see. I misunderstood your question. I have edited my answer.

Thomas Bormans Over a year ago

@syedfaizan Is this what you're looking for?

Syed Faizan Over a year ago

Thanks bro , you saved my day, forgot to comment yesterday, sorry

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