Mongo db - Querying nested array and objects

Question

I have the following document structure:

{
   "_id":"12345",
   "value":{
      "T":0,
      "v":[
         {
            "name":"JW",
            "cost":100
         }
      ]
   }
}

How do I query the name key? I tried the dot notation but without luck (I think it works for only two levels)

If you were by any chance doing a group by, you then need to use the $unwind operation on the value.v key before you can operate on the name/cost fields. — AP.
– AP., Commented Jan 6, 2017 at 20:35

JohnnyHK · Accepted Answer · 2014-10-27 15:17:58Z

38

It's not clear exactly what you tried, but this should work to find the above doc by name:

db.collection.find({ "value.v.name": "JW" })

Reference

edited Oct 27, 2014 at 15:17

answered Jul 24, 2012 at 21:50

JohnnyHK

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3 Comments

karel lahmy Over a year ago

Thanks, i'm sure it did not work for me, maybe i got the query wrong.

Samuel O'Malley Over a year ago

I don't think you can use the dot operator on an array.

JohnnyHK Over a year ago

@SamuelO'Malley I just updated the Reference link that better shows that this is supported with arrays.

AP. · Accepted Answer · 2017-01-06 21:35:34Z

20

You should use $elemMatch operator:

db.collection.find({
    'value.v': { 
        $elemMatch: {
            name: 'JW', // "name == 'JW'"
            cost : 100 //if you need "&& cost == 100"
        }
    }
});

Mongo docs

edited Jan 6, 2017 at 21:35

AP.

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answered Jan 26, 2014 at 0:07

neftedollar

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