Get elements from array

Question

I have an collections. Let's take one element from collection:

{
    "messages" : {
        "_id" : ObjectId("5503044be4b0e3d1aed29d15"),
        "body" : "Hello YOU!",
        "subject" : "sth"
     }
}

and now the tricky part. How to get elements from collection without wrapper. Like below:

{    
  "_id" : ObjectId("5503044be4b0e3d1aed29d15"),
  "body" : "Hello YOU!",
  "subject" : "sth"
}

@Michael The answer wasn't compleate. But I just voted up.

Quark986
– Quark986

2015-03-20 21:04:25 +00:00
Commented Mar 20, 2015 at 21:04 — Quark986
– Quark986, Commented Mar 20, 2015 at 21:04
What else is missing?

Sede
– Sede

2015-03-20 21:07:52 +00:00
Commented Mar 20, 2015 at 21:07 — Sede
– Sede, Commented Mar 20, 2015 at 21:07

Sede · Accepted Answer · 2015-03-21 20:22:46Z

3

It is simple you can use $project to add or reset a field within the document.

db.collection.aggregate([
    { 
        "$project": {
            "_id": "$messages._id",
            "body": "$messages.body", 
            "subject": "$messages.subject"
         } 
     }
])

edited Mar 21, 2015 at 20:22

answered Mar 20, 2015 at 17:39

Sede

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