CODEWITHSUNDEEP
mongodb
ixx
ixx

Reputation: 32267

How to retrieve a nested object?

I have a collection with documents like this:

{ 
    key : "bla"
    list : [
       {id:1}, 
       {id:2}
    ]
}

How do I get this object: {id:1} ?

I tried a query like this: db.myCollection.find({"key":"bla", "list.id":1})

it finds the entry, but returns the complete document instead of only {id:1}

Upvotes: 4

Views: 105

Answers (1)

ThePhysicist
ThePhysicist

Reputation: 1862

The $ operator is what you're looking for:

db.test.insert({key: "blah",list :[{id:1},{id:2}]})

db.test.find({'list.id' : 1},{'list.$': 1 })
#Returns:
#{ "_id" : ObjectId("521a78b342abf388fbaacf91"), "list" : [ { "id" : 1 } ] }

db.test.find({'list.id' : 2},{'list.$': 1 })
#Returns:
#{ "_id" : ObjectId("521a78b342abf388fbaacf91"), "list" : [ { "id" : 2 } ] }

If you don't need the _id of the document, you can exclude that too:

db.test.find({'list.id' : 2},{'list.$': 1 , _id: 0})
#Returns:
#{ "list" : [ { "id" : 2 } ] }

For more information, have a look at the documentation of the $ operator and read operations in general.

Upvotes: 4

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