CODEWITHSUNDEEP
mongodbmongodb-querynosqlaggregation
Leonardo
Leonardo

Reputation: 318

Get value of a specific field using aggregation in MongoDB

My document:

[
  {
    "_id": "5f969419d40c1580f2d4aa36",
    "users": {
      "[email protected]": "baz",
      "[email protected]": "baz2"
    }
  },
  {
    "_id": "5f9694d4d40c1580f2d4aa38",
    "users": {
      "[email protected]": "foo"
    }
  }
]

If i use this aggregate, i get two users. Ok. But how can i get only the value of "[email protected]"? Test in https://mongoplayground.net/p/3kW2Rw6fSjh

db.collection.aggregate([
  {
    "$project": {
      "users": {
        "$objectToArray": "$users"
      }
    }
  },
  {
    "$match": {
      "users.k": "[email protected]"
    }
  },
  {
    "$project": {
      "users": {
        "$arrayToObject": "$users"
      }
    }
  }
])

Upvotes: 1

Views: 41

Answers (1)

nimrod serok
nimrod serok

Reputation: 16033

You can add a $filter stage after the $match stage:

{
    $set: {
      users: {
        $filter: {
          input: "$users",
          cond: {
            $eq: [
              "$$this.k",
              "[email protected]"
            ]
          }
        }
      }
    }
  },

See how it works on the playground example

Upvotes: 1

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