select only subdocuments or arrays

Question

{
    \"_id\":{
        \"oid\":\"4f33bf69873dbc73a7d21dc3\"
    },
    \"country\":\"IND\",
    \"states\":[{
            \"name\":\"orissa\",
            \"direction\"         


        

Answer 1

Any query in mongodb always return root document.

There is only one way for you to load one sub document with parent via $slice if you know ordinal number of state in nested array:

// skip ordinalNumberOfState -1, limit 1
db.countries.find({_id: 1}, {states:{$slice: [ordinalNumber -1 , 1]}}) 

$slice work in default order (as documents was inserted in nested array). Also if you don't need fields from a country you can include only _id and states in result:

db.countries.find({_id: 1}, {states:{$slice: [ordinalNumber -1 , 1]}, _id: 1}) 

Then result document will looks like this one:

{
    "_id":{
        "oid":"4f33bf69873dbc73a7d21dc3"
    },
    "states":[{
            "name":"orissa",
            "direction":"east",
            "population":41947358,
            "districts":[{
                    "name":"puri",
                    "headquarter":"puri",
                    "population":1498604
                },
                {
                    "name":"khordha",
                    "headquarter":"bhubaneswar",
                    "population":1874405
                }
            ]
        }]
}