Return array of fields from subdocument

Question

can anyone please help I want to query mongo to unwind the array,and i am using mongdb native driver My collection document is as follow,Also please ignore my objectId its just for sample

{  
      "_id":ObjectId(123),
      "name":"Sam",
      "age":20,
      "hobbiesDetail":[  
         {  
            "description":"FootBall",
            "level":"20%"
         },
         {  
            "description":"Cricket",
            "level":"80%"
         }
      ]
   },
   {  
      "_id":ObjectId(124),
      "name":"Ted",
      "age":26,
      "hobbiesDetail":[  
         {  
            "description":"FootBall",
            "level":"20%"
         }
      ]
   }

And my expected output is

[  
   {  
      "name":"Sam",
      "age":20,
      "hobbies":"Football,Cricket"
   },
   {  
      "name":"Ted",
      "age":26,
      "hobbies":"Football"
   }
]

I just want to unwind my array and add a comma between hobbies description in one query, Thanx for any help

I don't like your expected output how about [ { 'name': 'Sam', 'age': 20, 'hobbies': ['Football', 'Cricket' ] }]? — Sede
– Sede, Commented Nov 15, 2016 at 4:54
No i cant because i want this to convert to excel,In excel it is not giving proper result for arrays — Parshuram Kalvikatte
– Parshuram Kalvikatte, Commented Nov 15, 2016 at 4:57
I suggest you return "hobbies" as array and do the remaining work client side. — Sede
– Sede, Commented Nov 15, 2016 at 5:05
Ohk Sir thanku,how can i query to get above result you suggested,as i cant use $concat i am using mongodb 2.8 — Parshuram Kalvikatte
– Parshuram Kalvikatte, Commented Nov 15, 2016 at 5:09

Sede · Accepted Answer · 2016-11-15 05:16:31Z

1

All you need is a $projection with the $map array operator.

db.collection.aggregate([
    { "$project": { 
        "name": 1, 
        "age": 1, 
        "hobbies": { 
            "$map": { 
                "input": "$hobbiesDetail", 
                "as": "hobby", 
                "in": "$$hobby.description" 
            } 
        } 
    }}
])

answered Nov 15, 2016 at 5:16

Sede

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6 Comments

Parshuram Kalvikatte Over a year ago

Why my hobbies field at top [ {'hobbies': ['Football', 'Cricket' ] , 'name': 'Sam', 'age': 20 }]

Parshuram Kalvikatte Over a year ago

i want it at last

Parshuram Kalvikatte Over a year ago

For that do i need to add another projection stage?

Sede Over a year ago

@Parshuram I have the correct order. Modify the order in which properties are displayed in MongoDB. You can always do this since you need a client side processing. What is your language driver?

Parshuram Kalvikatte Over a year ago

I am using nodejs,and now i am playing in robomongo its not giving me proper order as per my $project stage

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