Fetch data from nested mongodb collection

Question

I have a collection like the following. I wan to get the users data only where fb_user_id is 2001.

How can I do this in PHP?

{
"_id": ObjectId("5024db89b7ac1c900e000000"),
"title": "This is a title",

"users": [
            {
              "name": "John",
              "email": "[email protected]",
              "fb_user_id": "1000"
            },
            {
              "name": "Jack",
              "email": "[email protected]",
              "fb_user_id": "2001"
            },

        ]

}

I tried like this $data = $collection->findOne(array("title" => "This is a title", "users.fb_user_id" => '2001'), array("users")); But it will return all users information, I want only user information whose fb_user_id is 2001. Please help me — Binu
– Binu, Commented Aug 13, 2012 at 5:38

Alexey Ogarkov · Accepted Answer · 2012-08-10 14:25:59Z

2

Your could use the following mongodb query

{ "title.users.fb_user_id" : 2001 }

I case of more complex query you could use elemMatch query operator

{ 
   "title.users" : {$elemMatch : { "fb_user_id" : 2001, "name" : "John" } }
}

Something like that. Hope it helps

edited Aug 10, 2012 at 14:25

answered Aug 10, 2012 at 14:11

Alexey Ogarkov

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6 Comments

Alexey Ogarkov Over a year ago

Here is reference mongodb.org/display/DOCS/… But it`s also possible to find it via "title.users.fb_user_id" : 2001 $elemMatch is for more that 1 expression will update the answer

Peter Kirby Over a year ago

Oh, I feel so silly. I didn't have my glasses on when I read your comment the first time, and completely misread your answer. Yes, you are correct. I didn't notice the outer top and bottom brackets, so I wasn't sure what you were trying to accomplish with only a "title.users": {...}. My apologies!

Alexey Ogarkov Over a year ago

No problem, you actually help me to answer better for that questions. Thanks a lot.

Binu Over a year ago

I tried like this $data = $collection->findOne(array("title" => "This is a title", "users.fb_user_id" => '2001'), array("users")); But it will return all users information, I want only user information whose fb_user_id is 2001. Please help me

Alexey Ogarkov Over a year ago

You can setup fields set to return, but in any case it will be in your document schema, for example you have an object {a:{b:{c:123}}} and you run query findOne({"a.b.c" : 123 },{"a.b.c" : 1"}) here {"a.b.c" : 1"} is the setup which fields to return. But you will get in in the schema of parent object. Like "title" : {"users" : [ ] } and so on

|

Stennie · Accepted Answer · 2012-08-14 02:42:07Z

1

If you only want to return one match found within an embedded array (and not the rest of the array) you will need to either:

handle this in your application code (iterate the users array and find the matching element)
use the new positional operator support (SERVER-828) which will be available in the 2.2 version of MongoDB.

Example using the positional operator in the mongo 2.2 shell:

> db.mycoll.find({'users.fb_user_id':"2001"}, {_id:0, 'users.fb_user_id.$':1})
{
    "users" : [
        {
            "name" : "Jack",
            "email" : "[email protected]",
            "fb_user_id" : "2001"
        }
    ]
}

answered Aug 14, 2012 at 2:42

Stennie

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1 Comment

Stennie Over a year ago

NB: MongoDB 2.2rc0 release candidate has been available for testing since mid-July.

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