Mongodb: Query a json-object nested in an array

Question

I'm quite new to mongodb and there is one thing I can't solve right now:
Let's pretend, you have the following document (simplified):

{
   'someKey': 'someValue',
   'array'  : [
       {'name' :  'test1',
        'value':  'value1'
       },
       {'name' :  'test2',
        'value':  'value2'
       }
    ]
}

Which query would return the json-object, in which the value equals 'value2'?

That means, i need this json-object:

{
    'name' :  'test2',
    'value':  'value2'
}

Of course I already tried a lot of possible queries, but none of them returned the right, e.g.

db.test.find({'array.value':'value2'})
db.test.find({'array.value':'value2'}, {'array.value':1})
db.test.find({'array.value':'value2'}, {'array.value':'value2'})

Can someone help and show me, what I'm doing wrong?
Thanks!

Tushar Mishra · Accepted Answer · 2014-06-20 03:24:31Z

31

Using Positional operator

db.test.find(
    { "array.value": "value2" },
    { "array.$": 1, _id : 0 }
)

Output

{ "array" : [ { "name" : "test2", "value" : "value2" } ] }

Using aggregation

db.test.aggregate([
    { $unwind : "$array"},
    { $match : {"array.value" : "value2"}},
    { $project : { _id : 0, array : 1}}
])

output

{ "array" : { "name" : "test2", "value" : "value2" } }

Using Java Driver

    MongoClient mongoClient = new MongoClient(new ServerAddress("localhost", 27017));
    DB db = mongoClient.getDB("mydb");
    DBCollection collection = db.getCollection("test");

    DBObject unwind = new BasicDBObject("$unwind", "$array");
    DBObject match = new BasicDBObject("$match", new BasicDBObject(
            "array.value", "value2"));
    DBObject project = new BasicDBObject("$project", new BasicDBObject(
            "_id", 0).append("array", 1));

    List<DBObject> pipeline = Arrays.asList(unwind, match, project);
    AggregationOutput output = collection.aggregate(pipeline);

    Iterable<DBObject> results = output.results();

    for (DBObject result : results) {
        System.out.println(result.get("array"));
    }

output

{ "name" : "test2" , "value" : "value2"}

edited Jun 20, 2014 at 3:24

answered Jun 19, 2014 at 17:59

Tushar Mishra

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1 Comment

hitesh kaushik Over a year ago

how do I retrieve some of the parent fields along with the matching nested fields? I am looking for something like this in response: {'someKey': 'someValue','array' : [{ "name": "test2" , "value": "value2"}]}

Clíodhna · Accepted Answer · 2017-08-21 12:14:36Z

2

You can pass multiple find objects in element match for getting the exact answer.

db.test.find({'array':{$elemMatch:{value:"value2"}})

output: {'name' :  'test1','value':  'value1'}

edited Aug 21, 2017 at 12:14

Clíodhna

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answered Aug 21, 2017 at 11:10

IGDEV

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Comments

V_Singh · Accepted Answer · 2014-06-18 20:50:20Z

1

Try the $in operator like this:

db.test.find({"array.value" : { $in : ["value2"]}})

answered Jun 18, 2014 at 20:50

V_Singh

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1 Comment

Jonas M. Over a year ago

Thanks for your help, but unfortunately it doesn't work either. If I run this in the terminal, it returns the whole document

KARTHIKEYAN.A · Accepted Answer · 2018-01-09 05:39:41Z

0

Use $elemMatch and dot(.) to get your required output

db.getCollection('mobiledashboards').find({"_id": ObjectId("58c7da2adaa8d031ea699fff") },{ viewData: { $elemMatch : { "widgetData.widget.title" : "England" }}})

edited Jan 9, 2018 at 5:39

answered Mar 21, 2017 at 13:43

KARTHIKEYAN.A

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