Unwind for array of objects

Working with Data
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1

Hi everyone! I have a collection ‘users’ which contains documents having fields ‘name’ and ‘schoolid’. I have another collection ‘schools’ ,which contains ‘schoolid’ and ‘name’ (schoolid is not mongodb generated objectid). Now I want output which will have ‘name’ from users and another field ‘school’ which will contain ‘name’ from schools collection corresponding to the schoolid. Basically I have to join these collections based on schoolid(I am not using REF so I cannot use .populate). I am able to do so by following code: db.user.aggregate([{ $lookup:{from:“schools”,as:“school”,let:{schoolid:"$schoolid"},pipeline:[{$match:{$expr:{$and:[{$eq:["$schoolid","$$schoolid"]}]}}},{$project:{name:1,_id:0}}]}},])
But in this output I am getting ‘school’ as an array, containing object with a key ‘name’ and then value as the school name from ‘schools’ collection. But instead I want ‘school’ as a normal string which will directly display the school name and not along with the key ‘name’. I tried to use unwind but it simply converts that array into object. Please help me with the same. Thank you

2

Please provide sample documents from both collections so that we can experiment with your data.

Also provide documents showing the expected result.

3

Hi steevej, Thanks for replying.
here are the collections:

  1. Users collection
    [{"_id": ObjectId
    “name”: “Nikita”
    “schoolid”: “1”},
    {_id: ObjectId
    “name”: “Sunita”
    “schoolid”: “2”}]

  2. Schools collection
    [{"_id": ObjectId
    “name”: “Sheel niketan”
    “schoolid”: 1},{"_id": ObjectId
    “name”: “Vidya sagar”
    “schoolid”: “2”}

3.Output I want
[{“name”: “Nikita”, “schoolname”:“Sheel niketan”},
{“name”: “Sunita”, “schoolname”:“Vidyasagar”}]

4

Please read Formatting code and log snippets in posts and format your data in a usable format.

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