Convert array of embedded documents into array of elements in mongoDB

Question

What is the query or aggregation operator I can use to get this ?

Input:

{"_id": "id1", "contacts": [{"phone": "xxx", "email":"[email protected]"}, {"phone":"yyy"}, {"phone":"zzz", "email":"[email protected]"}] }
{"_id": "id2", "contacts": [{"phone": "aaa", "email":"[email protected]"}, {"phone":"bbb"}, {"phone":"ccc"}] }

Output:

(just need phone numbers, other contacts.fields can be dropped)

{"_id": "id1", "contacts": ["xxx", "yyy", "zzz"] }
{"_id": "id2", "contacts": ["aaa", "bbb", "ccc"] }

Ashh · Accepted Answer · 2018-09-13 13:53:01Z

1

Simply use $project aggregation pipeline stage.

db.collection.aggregate([
  {
    "$project": {
      "contacts": "$contacts.phone"
    }
  }
])

Output

[
  { "_id": "id1", "contacts": [ "xxx", "yyy", "zzz" ] },
  { "_id": "id2", "contacts": [ "aaa", "bbb", "ccc" ] }
]

edited Sep 13, 2018 at 13:53

answered Sep 13, 2018 at 13:39

Ashh

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3 Comments

Nar Over a year ago

Thank you Anthony. Sorry, just need little more, how do I get unique values into array? Seems some of Ids have duplicate phone numbers in collection.

Ashh Over a year ago

You can use $setUnion aggregation for that

Ashh Over a year ago

@Nar If you need any help in that then please ask a new question i will help you

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