To get the child of a collection in MongoDB, use find(). Let us create a collection with documents −
> db.demo305.insertOne( ... { ... _id: 101, ... FirstName : 'Chris', ... details : { ... "0":"102", ... "1":"10001" ... } ... } ...); { "acknowledged" : true, "insertedId" : 101 } > db.demo305.insertOne( ... { ... _id: 102, ... FirstName : 'David', ... details : { ... "0":"103", ... "1":"10002" ... } ... } ...); { "acknowledged" : true, "insertedId" : 102 }
Display all documents from a collection with the help of find() method −
> db.demo305.find();
This will produce the following output −
{ "_id" : 101, "FirstName" : "Chris", "details" : { "0" : "102", "1" : "10001" } } { "_id" : 102, "FirstName" : "David", "details" : { "0" : "103", "1" : "10002" } }
Following is the query to get the child of a MongoDB collection by the key −
> db.demo305.find({_id:102},{'details.0':1});
This will produce the following output −
{ "_id" : 102, "details" : { "0" : "103" } }