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Query to retrieve multiple items in an array in MongoDB?
To retrieve multiple items in an array, use aggregate framework. Let us first create a collection with documents −
> db.retrieveMultipleDemo.insertOne( ... { ... "UserDetails": ... [ ... { "_id": "101", "UserName":"John", "UserAge": 23 }, ... { "_id": "102", "UserName":"Carol", "UserAge": 21 }, ... { "_id": "103", "UserName":"David", "UserAge": 23}, ... { "_id": "104", "UserName":"Sam", "UserAge": 25} ... ] ... } ... ); { "acknowledged" : true, "insertedId" : ObjectId("5cd40c85edc6604c74817cf0") }
Following is the query to display all documents from a collection with the help of find() method −
> db.retrieveMultipleDemo.find().pretty();
This will produce the following output −
{ "_id" : ObjectId("5cd40c85edc6604c74817cf0"), "UserDetails" : [ { "_id" : "101", "UserName" : "John", "UserAge" : 23 }, { "_id" : "102", "UserName" : "Carol", "UserAge" : 21 }, { "_id" : "103", "UserName" : "David", "UserAge" : 23 }, { "_id" : "104", "UserName" : "Sam", "UserAge" : 25 } ] }
Following is the query to retrieve multiple items in an array −
> db.retrieveMultipleDemo.aggregate([ ... {$unwind:"$UserDetails"}, ... {$match:{"UserDetails._id":{$in:myIds},"UserDetails.UserAge":23}}, ... {$group:{"_id":"_id","UserDetails":{$push:"$UserDetails"}}}, ... {$project:{"_id":0,"UserDetails":1}} ... ]);
This will produce the following output −
{ "UserDetails" : [ { "_id" : "101", "UserName" : "John", "UserAge" : 23 }, { "_id" : "103", "UserName" : "David", "UserAge" : 23 } ] }
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