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Querying on an array of objects for specific nested documents with MongoDB?
To query on an array of objects for nested documents, use find(). Let us create a collection with documents −
> db.demo763.insertOne( ... { ... _id:1, ... CountryName:"US", ... "studentInformation": [ ... { ... StudentName:"Chris", ... }, ... { ... StudentName:"David", ... StudentAge:22 ... } ... ] ... } ... ); { "acknowledged" : true, "insertedId" : 1 }
Display all documents from a collection with the help of find() method −
> db.demo763.find();
This will produce the following output −
{ "_id" : 1, "CountryName" : "US", "studentInformation" : [ { "StudentName" : "Chris" }, { "StudentName" : "David", "StudentAge" : 22 } ] }
Following is how to query an array of objects to fetch specific nested documents −
> db.demo763.find({}, ... { ... studentInformation: { ... $elemMatch: { ... StudentAge: { ... $exists: true ... } ... } ... } ... })
This will produce the following output −
{ "_id" : 1, "studentInformation" : [ { "StudentName" : "David", "StudentAge" : 22 } ] }
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