CODEWITHSUNDEEP
mongodbmongodb-queryaggregation-framework
Chain
Chain

Reputation: 15

How do access values in a nested documents in MongoDB?

I am trying to find the average sell of each console xbox, ps4, and wii. I am working with nested documents, and I try to access type to filter "sell" using db.console.find({"market.type":"sell"}); but I end up getting "online" type values as well.

Document 1:
_id:("111111111111111111111111")
market:Array
   0:Object
      type:"sell"
      console:"Xbox"
      amount:399
   1:Object
      type:"online"
      console:"PS4"
      amount:359
   2:Object
      type:"sell"
      console:"xbox"
      amount:349

Upvotes: 0

Views: 44

Answers (1)

krishna Prasad
krishna Prasad

Reputation: 3812

Since you need to filter the sub-documents from a documents so simply find will not work to filter the sub-documents.

You have to use aggregation pipeline as below:

    > db.st9.aggregate([
    {
        $unwind:"$market"
    }, 
    {
        $match: {"market.type":"sell"}
    }, 
    {
        $group: {_id:"$market.console", "avg": {$avg:"$market.amount"}, "count": {$sum:1}, "totalSum": {$sum: "$market.amount"} }
    } 
])

Output: 

{ "_id" : "PS4", "avg" : 300, "count" : 1, "totalSum" : 300 }
{ "_id" : "Xbox", "avg" : 359, "count" : 3, "totalSum" : 1077 }
>

For more reference on aggregation pipeline check below official mongo db documentations:

  1. $unwind
  2. $match
  3. $group

Upvotes: 2

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